Hi.
Don't flush anything! (If by flush you mean the toilet). I would advise that you take your existing fish and take them back to your LFS or rehouse them until you can sort out your cycle. If you absolutely can't do that, then you're in the middle of a fish-in cycle and you're going to have a lot more work on your hands.
A few important questions:
1) How big is your tank (in litres or gallons)
2) What sort of filtration do you have, and what make/model is it?
3) What are your water stats? (this is the most important one - it sounds like you only have test strips, which really aren't good enough for what we need to know to help you properly. You need to get yourself a liquid test kit (API Master Test Kit or similar) and we will be far better placed to help you.
If you can get rid of the fish, do so at the earliest opportunity, and then come back and read up on here on fishless cycling. If you absolutely, 100% cannot get rid of them, then do a large volume (75-80%) water change *now*, and then do this every day for the next week, for starters. This should prevent any more catastrophic fish deaths in the near future, until we can work out what stage of your cycle you're in from your water stats.
Without the information above (1-3) we can't really help you in massive depth, and most importantly we need your water stats (ammonia, nitrite, nitrate) as that's the most important thing to know.
Edit: Don't bother with the bacteria solution - for the most part, it's basically just a gimmick with no live bacteria in it, unfortunately. It can't do any harm, though, what you've added already, just don't waste your money on any more
