I imagine your cycles would be off from the birth control as it is likely still in your system. In regards to trying to get pregnant, try to think of any goals that you have at this age that would maybe interfere with motherhood. If you want to go to school or start a career getting pregnant right now might not be a good time. Glad you posted here though and keep us updated on your situation.
You don't ovulate a week after your period. Ovulation happens at different times for everyone and there are ways to track your ovulation, but I won't help a teen figure that out and get pregnant. Have you really thought about what having a baby entails? How much money, time, effort, goes into raising a child. Do you have a stable job with a good amount of income? Do you have money saved up in the bank? Are you in a very long term relationship or preferably married? Do you have health insurance? Do you have a good, safe place to live? Can you afford a baby? (rent, gas money, car insurance, phone bill, utilities, health insurance, food, money for diapers, formula, baby food, car seat, stroller, toys, etc.) Don't make any quick decisions unless you know exactly what you are getting yourself into.