Dull lower abdominal pain.

I'll start with some info. I am taking hormonal birth control, my periods are regular and 5 days long, my boyfriend and I have unprotected sex once a month if that (we live with my parents), I'm 20 yo and I'm overweight if that makes a difference. I also smoke (about 3 cigarettes a day)

Okay, so whenever we have sex, especially when I'm on my period, I have this dull abdominal pain. When I went to my gyno last april, I found out I had chlamydia. I was given two pills to take and that was that. I never went back to the gyno to make sure the chlamydia was gone (oops) but I felt alright for a while. It started happening again recently. Of course I'm going to schedule an appointment with my gyno soon, but I just want to know if anyone else has this issue.

The last time my boyfriend and I had sex was Feb 13th (3rd day of my period).