Have you gone to the doctor for your irregular periods? If you have tested for Pregnancy then chances are you are not pregnant. Unfortunately, since we are not doctors and your symptoms can be that of many things-- it would be a good time to get a complete physical exam done.
It may also be a good idea for your boyfriend to see a specialist to see if he can have kids (if you would like children in your future). Remember that just because you or his ex girlfriend haven't and didn't get pregnant, that's not enough to assume you can have unprotected sex without it being a possibility.