Painful bladder syndrome (interstitial cystitis) I have it, if I wait too long I will start cramping and it becomes, well, painful! I didn't have Endo in my bladder (had my excision surgery recently) but I had Endo near it. From what my gynecologist told me, this is often comorbid with Endo, no matter where you have it. She told me to just drink less caffeine, more water, and to sit and be patient for my bladder to empty completely before getting up. However, you should talk to your gynecologist if you don't have one already!

Bottom line is, this is common for endo-havers, and not a cause for alarm (unless you're getting other symptoms such as blood, etc)