Your fish are dying because your filter has not cycled and you haven't been keeping the water clean. The various diseases etc are happening because of this one key issue of water quality so you really need to sort that out rather than just chucking in multiple meds and hoping for the best.
There's a really good pinned topic on weekly tank maintenance here [topic="0"]http
/www.fishforums.net/index.php?showtopic=171045[/topic]
That explains how you clean your filter (in old water, not tap water) to preserve the beneficial bacteria on the filter sponges that keep your water free of Ammonia and Nitrite (poisonous to fish).
Your tank will take around four weeks (minimum) to cycle (that is, build up the beneficial bacteria ) and until it does this your fish are going to be under even more stress. If you can get hold of some mature (i.e. used, grungy) filter media (like a piece of the sponge) from a healthy tank that has been up and running for a couple of months, you can put that in your filter and it will speed up the process dramatically (and thus lessen the stress for your fish).
You need to be prepared to do daily water changes if that's what it takes to keep your ammonia and nitrite down during the cycle, otherwise your fish may die.
I don't mean to sound harsh but you need to get organised if you're going to save your fish. Buy a test kit immediately -- a decent one like the API Master Test kit -- and get your water stats on here so people can help you. Test your water every day if you can, and you'll be able to chart the progress of your cycle. There are a lot of very knowlegable people on this forum -- they've been really helpful for me -- so keep asking questions if there's anything you don't understand.
If you don't think your filter is working properly, buy a new one. You can get cheap secondhand ones on ebay. If money is an issue, ask your Mum for a loan. Tell her otherwise she's going to have a tank of dead fish stinking the place up.
This is going to be hard work for the next few weeks, but once your tank is cycled and healthy again it will be worth it.
Good luck to you and your fish