Birth control and pregnancy..PLEASE HELP!?

Ok so I started my birth control 3 1/2 months ago for the 1st time ever. After the 1st month I had a period that was normal. However I haven't had one since. Im really bloated right now and I have had menstrual cramps like I always do right before I start but nothing happens, no period. I know this can be normal while on the pill but I have also been really nauseous. Could I be pregnant? I know for the 1st couple of months you have to be careful but I figured since I wasn't having a period that i wasn't ovulating either. Im worried that im pregnant because I definitely cant have another baby since my son is only 15 months old and Im not ready for that again. I do know that my digestive system is a little messed up to because I got sick at a restaurant, and had diarrhea for 12 hours. Could I just be constipated? Please help! I cant go to the docs because my insurance doest kick back in for another 30 days. Please give me some advice!! Thanks!!!