HELP... What do I do?

I used to have irregular periods as a teen, until I turned 15 when I started the pill. I was on it for 2 years to regulate my periods and they have been bang on time every month since I stopped. Unless I was stressed then I'd be 3 days late maximum... I'm now 11 days late for my period and I haven't had cramps and I'm feeling kinda sick, not sure if mother nature is about to make a river come out of me or if I caught a bug! Either way not sure. I havent had sex for 2 months now and I'm not sure what to do, has anyone ever had anything like this? As I'm not sure if I could be pregnant as I had a very light period last month and now, nothing... Any advice?