I'm having unusual pains while I'm on my period..

Up until lately about for a couple months now I’ve been having a hard time going to the bathroom every single time I’m on my period. I get these unusual pains that I can’t even describe and it’s even hard for me to describe where exactly the pain is because it’s so intense.. All I know for sure is that when I’m going to the bathroom to take a crap I get this weird intense pain my anal or genital area as the poop is coming out. Mid way before the feces even comes out and drops into the toilet bowl I get this pain. I believe it happens when I push too hard (pushing as in pushing so that the poop comes out). I can’t describe it well, but I believe that my muscle in my genital area seems to be tensing to the point where I can’t take the pain. To the point where it makes me want to scream and cry every single time. When I do get these pains I immediately jolt my entire body as if it jumps on it’s own because the pain is too much too bare. Every single time I get that pain my body jolts.

As a side note I am a 18 year old girl, who happens to have Genital Herpes not from sexual intercourse. (I’m not exactly sure how I got it, but for one thing I know that I didn’t have sexual intercourse to acquire it.) BUT I have had sexual intercourse.

I don’t know if having genital herpes has anything to do with it, but this has never happened before. I’ve had genital herpes for a couple years now, but this pain has only been happening for a couple months. This pain only happens when I’m on my period and when I’m taking a crap. It doesn’t happen when I’m peeing. As another side note I have a normal period. I get it every single month. I do not take any birth control pills either. But I have taken Plan B once. I doubt that Plan B has anything to do with this because I’ve had pains way before I even took Plan B.

I honestly do not know what is happening..