Irregular bleeding

Before I got married I was a Virgin and my periods were consistently 7 days long. Now that I’m married And really since we started having sex my periods will be much lighter and last 2 or 3 weeks. I went to my Gyn and got a pap done and she said it was clear. That the bleeding was coming from my uterus not my cervix. I have no idea what this could be but it’s been going on for nearly 5 months now. Help!!! Any info could help!