My Period Is Usually Very Heavy, I Can Wear The

My period is usually very heavy, I can wear the ultra tampons & soak them within 2 hours. (sorry for the tmi) However now my period is much more lighter & I'm not having to change my tampon but 3 or 4 times a day, which normal for me is changing about 8 to 10 times a day. But my cramps are probably bout the same as if it were my normal period. I did have unprotected sec a few days after my fertile days. Is it normal for your period to just change like this? Or could it be possible I can be pregnant?