If you DTD the day you got your positive then you should be in with a good chance, that's when they say to do it! DTD after you positive O is a bit useless really, unless you just in the mood for a bit of random BDing!

Have a look at Fertility Friend, lots of good info on there and you can chart your cycles too. I found it really helpful when we were TTC DD. Have you visited the TTC (trying to conceive) threads in here too? Lots of info and girls in the same position.

I hope you get your BFP soon!!