Three to four days after your last period you're more likely to be fertile. That is the best time to conceive and start taking prenatal vitamins to get yourself in the right track
And be aware, depending on the kind of birth control you were on (and for how long), it may take several months for all the excess hormones to leave your body and for you to start ovulating normally again. Some women get pregnant if they miss s single dose of birth control; others it takes up to a year off BC before they conceive. I picked up a book called Taking Charge of Your Fertility, and it provides TONS of excellent information! It also teaches you how to check your cervical fluid and monitor basal body temperature the determine the exact day you ovulate. The road to conception can be a hard, painful road, and it sounds like you've only just begun. Give it time, read, research, learn all that you can and good luck!