please ease my mind

So I’ve had my mirena iud for a little over a year now and during the time had a bf that I had unprotected sex with but I’ve had pretty regular periods with a decent flow since then. I recently started having unprotected sex with my current fwb for about a month and a half now I’ve had one period with a decent flow last month, but this month my “period” came 2 days late and is so light that I have to stick toilet paper up there in order to wipe the discharge and it’s a really dark color. Please tell me I’m just tripping out and not pregnant.