My body is confusing me

I'm 3 months post IUD insertion so I do have it. My month and a half of off and on spotting has stopped. During that time and still now I would have unprotected sex about twice every day to every other day with my BF. Had some severe pelvic pains; more cysts ruled that out and was not pregnant since they still checked. This was about 2 weeks ago.

Now I've started extremely lightly spotting not like before and my nipples are really sore.

Please tell me this is an IUD side effect 😂😂