I've taken Diflucan several times, and it always seems like I have to use Monistat with it in order to fully cure the infection. My doc says this is okay and pretty common. And yes, it does seem to get worse for a day or so before it gets better.
If you're not feeling better within 48 hours of taking the diflucan, I'd recommend buying Monistat too. The 1 or 3 day treatments NEVER work for me, so as much as it sucks, use the 5 or 7 day. I also take acidophilus pills and eat lots of yogurt. That seems to keep them away. Good luck!