A little worried 😖

T
Hey guys! This is going to be a long post but please bear with me!!
My name is Tara and I've had this app for a few months now. I don't ever post on here, I usually just scroll through and like to read others posts and comments but I'm a little worried about stuff and thought I would make a post and ask if anyone had advice/a likewise situation/or if there's a nurse or doctor on here who could possibly help me figure stuff out. So yea, I'm 19, less than a month away from 20, and sexually active with my 20 y/o boyfriend. We've only ever been with each other and we are very very careful when we have sex to make sure there aren't any accidents (we use condoms and he pulls out way before he cums) but this last time was kind of scary. Everything started out fine and I felt alright being on top but as soon as we switched positions to me being on my stomach, I got this awful, shooting pain inside of me. At first it wasn't too bad, just a slight discomfort I could deal with but then it became unbearable. I don't ever have a problem with any position, especially this one bc it's actually my favorite, but this time it hurt real bad. We stopped and I went to the bathroom to check if it was a cramp from me starting my period because I get awful debilitating cramps when my period starts but I wasn't bleeding or anything. Afterwards the pain subsided and was this weird feeling of like a period cramp/running cramp/I need to fart really bad but it won't come out/dull type of pain. I don't know what happened and I'm honestly scared. I would go to the doctor but I kind of can't because I don't have my own car and I can't tell my mom I'm sexually active or she'll kill me. I'm late on my period (which I don't think is of too much concern seeing as how I have an irregular period) and I have bad anxiety so I've been stressing a lot lately and I don't know if all of this could have happened because of my stress or me being late or whatever. 
Thank you if you read all of this and thank you if you comment to help!!