I have been thru the same thing with birth control in the past. I have taken several kinds of pills, the patch oand the depo shot. Usually I find that if I start and stop birth control, I may have period and I may not. It may be extremely heavy or very light. I would not be concerned about pregnancy at this point. Depending what kind of BC you were on and your own body, it could take sereval months before things get straightened out. If you want to be pregnant, I wish you the best. If not, hang in there. I think that you period will get back on track soon. Talk to your doctor if this really bothers you.
If your period has been off before than one cycle of birth control isn't going to regulate it. Best thing to do is see a doctor and try to figure out what is going on. Its possible that you are pregnant try waiting until your period is due and test again or get a blood test done. I know you dont have insurance but they have free clinics for things like that.