I have been on the pill for 9 months now and have never had any problems. Me and my boyfriend have sex without a condom however he always pulls out. I have heard stories about women having their withdrawal bleed/period even when they are pregnant so I can't help but worry. I have noticed my tummy has started to stick out a little bit, I'm not fat (5'5 and 119 pounds). I don't know if my belly is starting to stick out due to my bad eating habits or if I am pregnant. This probably sounds silly but I am probably the worlds biggest worrier...

Withdrawl isn't a form of birth control... but the pill is. However with that said... no form of birth control is 100% effective (not even the pill) so yes it is possible you are pregnant. You will have to take a test to find out.