rash??

Okay so recently I have been having this rash on the back of my legs and even a little on my a**. It would usually pop up randomly and it doesn't itch or even hurt. Sometimes it disappears after a few hours sometimes it lasts a couple days. I just noticed this like a week or so ago. Does anyone know what it is? My bf came in me two days after my period (when he came in me it was the 13th of January) and I'm worried it might be from pregnancy. I read online tht some girls get rashes. I am worried tho cuz some said rashes during pregnancy is a bad thing. Idk for sure if I am pregnant or not, but I have a had a few symptoms such as; extreme fatigue, bloating belly, light cramps, my breasts look larger, nausea, and I'm almost always hungry 😋. Anyways, can anyone help me plz.