Cramps with full bladder?

I noticed that every time my bladder gets super full i start getting similar cramps to period cramps it hurts my lower belly, back and groin for a few mins or seconds. I drink a lot of water throughout the day & The only reason why I don’t empty my bladder is bcs im sitting down most of the time due to work or at night when im in bed & with those two things i don’t feel my bladder get full unless i stand up or get the pain. Im 30 weeks and i heard that a full bladder can cause BH but idk. Anyone had something similar???Or any thoughts??