If you had sex two months ago, have had a period, and haven't had sex since your last period, you are probably not pregnant.
It's really, really rare to have a period while you are pregnant, but it can happen in the first month of pregnancy, or the first "period" could have been implantation bleeding (but I doubt it.)
If you are sure it was a period that you had, then don't worry. You could just be stressed out or something else besides pregnancy could be delaying it.
If this doesn't help you, you can always take a test. That never hurts and will give you more peace of mind.