Hi,
Well I am a slow reader and this post has taken me all night to read! (slightly exaggerated). But, biokid I really think you should take on board all of the comments added. In my experience the majority of people that post on topics like this are just looking out for you and your pets. Also in your first quotes you actually did say 'help' which I would interpret as someone wanting advice/opinions regarding your situation.
Everyone else tho lets not forget that biokid is a 15 year old kid so perhaps we should remember what we where like at that age (that's not meant to sound patronising in anyway biokid).
As for signs to see when your dog is in heat...
The two main signs are swollen teats and vaginal area, bloody discharge, increased temp and a very definite sign would be increased levels of certain hormones (but obviously you cant test for those! lol). But actually its more important to know what stage of season your ***** is in, as its only at the estrus stage that the ***** could get pregnant (actually they can get pregnant during any stage but they are considerably more fertile and receptive to males during estrus). The estrus stage can be recognised by the bloody discharge from her girly area turning a lighter colour (like watered down blood) and the ***** standing for males to mount her (a good trick is to scratch the top of her bum, if she is in estrus she will stand firm and lift her tail to one side, although this isn't by any means a definite sign as my spayed ***** still does this lol). During this stage and in fact throughout her season she can be walked but strictly on the lead. Other entire dogs will notice her but will get over it fairly quick and if off the lead should have a certain amount of training under their belt. You can also get a spray to hide shes in season if the nappies are a bit much, which I wouldn't blame you lol!
With regards to breeding her...
3-4 years is still too old for a first litter, the first should be on their second full season (as they can have phantom seasons), or around 21 months with a 3 month gestation (pregnancy) therefore their first litter born will be a 2 years old (approx). This gives them enough time to mature and develop correctly, litters before this are not a good idea as it takes a lot of energy into breeding and pregnancy that should be being used for growth, also would your dog be mentally ready for such a responsibility.
It is also equally, if not worse to wait past 2 years, with every season there is an increase risk of pyometra which is a very serious infection of the uterus that can KILL your ***** very quickly without any obvious symptoms. Not to mention other hormone imbalances that can occur due to being entire but not mated (These tho are NOT reasons to breed your dog quite the opposite) I think spaying your dog is a very good idea, based on the health implications mentioned. Also if you did want to breed your ***** you would need to get a few things checked out for example hips, elbows, possibly eyes and deafness all of which are genetic and therefore your dog may not suffer from but may genetically carry. Also there are other genetic conditions that will be breed specific to your ***** that you will need to check. Most of these can be carried out in the uk now but are still new and eyes and deafness I believe still has to be done in America which is VERY expensive we are talking 1000's of pounds!
I think its lovely that you want to breed dogs but please wait for the correct time for it, do some research talk to people and maybe when you are older you can breed another dog. (I don't think I need to mention possible costs if/when pregnancy goes wrong and I say when because many first litters do go wrong esp. if the ***** is 4+ years old.) Also are you prepared to lose you pet if it does all go wrong because that is also a common problem with older mums.
Well that's me done I think! I would like to mention that although I don't have any first hand experience with breeding dogs I am a fourth year veterinary student with lots of hours of lectures behind me and first hand experience of when it goes wrong! I have also carried out work experience at a number of shelters including the RSPCA and I would hate to see any more dogs in there unnecessarily.
Please don't think I am trying to scare or bully you into a decision because it is your family decisions after all, but maybe you should wait then the whole experience can be a happy one! If you would like any further information or advice please don't hesitate to pm me of post on here.
I hope that has helped you make the right decision.
Oh and thanks for reading it took my just as long to type this as it did reading it back good old dyslexia! lol! x