Bleeding after sex with an IUD

I have been having issues with bleeding after sex. I have an IUD so I’m worried it might be displaced. I unfortunately do not have any health insurance so seeing a doctor isn’t really an option for me. Recently I have only been getting my period once every few months, and the bleeding after sex happens when I’m about two weeks late according to this app (it’s still set that I should get my period every month). I haven’t noticed it happen in the weeks leading up to my period, only after it’s late. I do not think it is my period though because I only bleed for like 10 minutes, and it’s really light in color. I usually feel nauseous afterwards and a slight cramp. I’m so confused. Does anyone know what this could be?