bleeding after sex without a condom

hi ! bit of a strange problem I’m having, haven’t been able to find any answers on the internet for this one !

I have an iud and I also usually have sex with a condom. Since having my iud my period has been pretty minimal, usually have it lightly every couple of months or so. However, I have noticed a couple of times that after having sex without a condom, I experience some light bleeding (potentially from vaginal tears I assume) however this then subsequently turns into kind of my period ? like I will end up with my period the next day. This has happened probably 3 times, and doesn’t seem to happen after having sex with a condom. I’m not sure if it’s just a coicindence that I get my period very soon after having sex without a condom, if the sex triggers this in some way, if this is related to my iud, or if it’s a coincidence.

I should add that the periods that have happened right after sex without a condom are regular in terms of duration and consistency compared to my usual periods.

Anyone had this ??