Cervix issues?!

So I'm on my period and I sometimes I get this unbearable pain in my abdomen but it's not pain like cramps it's more like pressure. But the pressure gets really intense that I start sweating and shaking. Is this Normal? Especially sometimes when I sit down to use the restroom I feel like my cervix is openening. Like the pain from the pressure gets so intense when  I'm sitting down that it makes me jolt up.can anyone explain this or help me understand what's happening please?