period cramps :( help?

somebody help. I’m 15 and I’ve had my period for 3 years now. I know my body well, so I know when mf aunt flow is about to show up. and my period is excruciatingly heavy. I fill night time extra large pads in a few hours and I can’t use tampons unless their minis bc I can’t exactly... fit it. in. my period normally starts on the 2nd thursday of the month and goes from 8 days to 10 days. but every single fricken time my period comes, I’m in such agony and pain with period cramps. I can’t sit because I get baddd pain in my rectum. I can’t stand or walk because of the cramps sometimes because they hurt so bad, I’ll end up hunched over. and maybe I just need a good bathroom break? no. I try to but then I get stitch like pain in my stomach and I can’t.. go. to the toilet. I take naprogesic tablets for my cramps but even then they barely work and I take a shit tonne of panadol. on weekends I use a heat pack and a hot waterbottle.. nothing works!! please. somebody help :((