IUD Spotting & Pain After Male Ejeculation

I received my IUD in November on 2019. It’s started to settle in being that I haven’t had my period in about 3 months now. When I did get them after my IUD they were very light and lasted 2 - 3 days on and off.

I’ve had sex with my boyfriend twice already. Once last week and again two days ago and he came in me both times. On Saturday before we met on Sunday I noticed that I had severe stomach pains. They started to go away halfway through the day and then we had sex again and the pains came back. Now it’s Tuesday, ive noticed creamy discharge and I’ve noticed some bright pink spotting. I’m assuming my period is coming but I wanted to see if anyone has experienced this as well?

Also is it normal for you to hurt after your partner ejaculates inside of you? Why does it hurt so much? I literally felt like I was carrying a watermelon all day and at times I couldn’t breath.