Bloated Betta With Cyst

Hello i am having trouble with my betta for a few days now and i need help determining what is wrong.
 
About five days ago my betta lost its appetite and began to get bloated but he was still acting normal. now i figured he probably got a bit of constipation so i gave him some cooked crushed peas, yet he wouldent touch them. the next day he began to get shy and constantly hid. on the third day not only was he not eating and bloated, a sore, about the size of his eye opened on the side of his abdomen. it is at this point i decided to take more serious action and i moved him to my quarunteen tank. (he was a community tank betta). in the quarantine tank i added a tiny amount of aquarium salt and another pea to treat the constipation and an antibiotic to prevent the sore from getting infected. ( thought maybe the sore was caused by another tankmate picking on the sick fish). however yesterday i noticed that on top of not eating and being bloated, the sore had now puffed up into an orange looking cyst and he has long stingy white poo. i researched online thinking now perhaps the betta is not suffering from constipation but another ailment, however i keep turning up answers from fungus to bacterial to parasites. so now i dont know what the problem is. currently there is no improvement and the betta is getting worse. i am starting to get worried as he is now coming up on a full week without eating. any ideas would help.
 
Summary of Symptoms: Bloated, Not eating, Large orange cyst on the side of the abdomen, lethargic, white stringy poo. colouration: normal, fins:normal. 
 
Current treatment: salt, antibiotics
 
Set Up:
Original community tank
Size: 20 Gallon
Description: live planted, with 1 gourami, a few barbs/dwarf rainbows, handful of bottom dwellers.
Heated: yes-25*C (77*F)
Filter: Yes
Air pump: yes
pH: ~6.5
 
quarantine tank:
size: 1.5 Gallon
Heated: Yes
Air pump: yes
 
Again, any ideas would be much appreciated. i will try to upload a picture later if i can
 
 

Can you get a picture of the issue?  That would go a long way toward helping to solve the issue.  One thing I see is that with the community you keep him with he is going to be in stressful conditions which lower the immune system.  Gourmani and Betta are not good tank mates since they are both aggressive fish and both are surface breathers meaning they inhabit and would therefor "fight" for the same area of the tank.  Another thing is the temperature is a bit low for the betta in the community tank as well.  Ideal temp is no lower than 78F but more like 80F to be the best he can be.  
 
Make sure you keep the small tank heated and very clean.  I am not as concerned about him not eating as much as I am the other issues.  I can not really advise treatment though without a look at what is going on.

ok so here is a picture, i apologize i couldn't get a picture directly on the side of the betta. the orange mass behind the side fin is the cyst. he wasnt pooing at the moment so i dont have a picture of that. i can keep trying to get better ones. 
 
As for the betta gourami interaction, I have never had a problem with those, two. it is a female gourami so i think that helps, they have never acted aggressive towards each other and infact could be seen many times schooling and hanging out with each other.

Poor thing.
What the name of the antibiotic you are using Star.
Does the cyst feel hard to the touch, or soft and filled with fluid.
Is the cyst smooth in texture and  not resemble a cauliflower.
Are the scales of the fish starting to stick out.

Definitely see if you can get a feel for the cyst.  Hard or soft, smooth, or cauliflower texture;  The answers to these questions can help us determine what might be the issue.  Does the "cyst" change shape or size?

its hard to get the exact texture of the cyst, it feels like a lump of tissue, not too much different in texture from the body of the main betta. it is not cauliflowed as far as i can tell. the outside layers of the cyst seem to be made of loosely attached dead tissue and underneath there appears to be a smoother round component. The cyst has not changed shape or size since it appeared two days ago.
 
the antibacterial im using is Melafix by API, i believe its just a general purpose antibacterial. Also, the scales are normal with exception of the few around where the cyst is, they look as though they have beem disloged a bit. 

All you can do really is try anti internal bacterial medication by interpet. Which won't interfere with your bacteria colony in your filter.
You can double dose in severe cases. If the fish breathing is fine. The fish is in isolation.
The scales  do tend to lift around lumps and bumps. Just make sure that you can't see any visionable parasites around the lifted
scales.

ok, i am also adding a few new pictures, hope these can confirm your thoughts

Keep a look out for the lump getting bigger, or changing colour.
Lumps that suddenly appear are  usually bacterial.
 
Some information on tumours. Just hope it isn't one.
 
 
 

Tumors

 

 



Symptoms:

Fishes with tumors have distended bodies or lumps on the skin. Unusual growths or swellings may occur in any part of the body. If they occur in internal organs they tend to cause firm, noticeable swelling to the general body shape. Tumors are usually confined to one area of the fish but they will continue to grow over time, weakening the fish until death occurs.
 


 



Cause: 

A variety of environmental factors such as chemical pollution or severe viral infections. A predisposition to tumors may be inherited from a fish's parents.
 


 



Treatment: 

There is no chemical remedy for this condition. Surgical removal of tumors can be attempted, but there is a high frequency of recurrence.
 
Fish Diseases Net

This is a better medication and have used it in the past.
But I would only suggest using the medication in isolation as it knocks bacteria colony in your filter.
 
 
 
http/www.seahorseaquariums.com/JBL-Furanol-2-20-Tablets//1509

Sorry only just noticed that your location is Canada.
Maracyn plus,but only use in isolation. 

ok, the betta is currently in isolation now. thanks

Good Luck.

the betta died last night thanks for your help and input anyway

Sorry for your loss. Bless Him.

Sorry I forgot to ask in the previous post.did the growth burst?
I would preform a few daily water changes just to be on the safe side.
As growths can leak fluid into the water.