quitting birth control for two weeks can definitely make a woman fertile again. When was her last period? How long after her last period was it that you had sex?
Generally (and I'm REALLY generalizing here) a woman's menstrual cycle will leave her fertile only a few days out of the month. This day is 2 weeks after her period, plus or minus anywhere from 1 day all the way up to a week or more (so some women are fertile for just day 14, others can be fertile anywhere from day 7 all the way through day 21). It is likely that your girlfriend is normal (statistically, that is). If you didn't have unprotected sex 2 weeks after her period (and a few days before and after that day), chances are that she is NOT pregnant. This is NOT gauranteed at all, but the chances statiscally are lower.
Now that I've spewed out everything I can remember from my human reproductive and sexual behavoir class in
college, I can offer one peice of advice: go see a doctor. If you want to avoid a doctor, go here:
http://www.plannedparenthood.org/
If she missed a period, or she's close to when she should start her next period, there are pregnancy tests she can take that will tell her (even before a missed period).
Last but not least, don't let her drink or smoke until she knows for sure.
Oh yeah- if it wasn't obvious, my advice was to test for her being pregnant. It's possible that the birth control could be causing her pain and bloating, but I'd be safe and find out for sure.