please help???!!

Me
Sooo I have an IUD and I had it put in in November, I'm 18, I've never had a child or pregnancy so there was a chance it would be expelled. I went for following check up appointment and the lady doc said everything was good. So I'm good there and I'm pretty sure it hasn't come out with my period. I've just been spotting. The spotting slowed down enough recently that I felt comfortable enough to have sex with the boyf. So we did. And we don't go super rough or anything, just moderately, but I bled really bright pink blood afterwords. Not a whole lot but enough throughout the day to get me worried. Then it stopped after two days and we had sex again, twice, and the same thing happened! This was two days again and I'm still bleeding a little. I've had sex before this many times so I don't understand why I'd be bleeding like this recently. I'm not in pain or anything:/  Can anyone explain why or what it could be a sign of??? (Also, with the IUD we don't use condoms anymore if that's info that is important)