Uterus pain after period

I'm 16 and not sexually active I have really no reason for this to be happening but my low abdomen hurts like a stabbing pain and my period ended on the 1st so is not cramps can anyone tell me what this is it's right in the middle of my low abdomen and I noticed it hurts worse when I have a full bladder I think it's because it pushes on it but it still hurts after I go to the bathroom so it's probably not my bladder

do you have any idea what this is

thanks