Pelvic pain since last night. maybe constipation/gas, but moved bowels once today. internal pain sitting, urinating & trying to defecate. ideas?

You're right ...: ...maybe constipation, but other problems in the lower colon or bladder/urethra or even uterus and ovaries would have to be considered. Pain like this that goes on for longer than a day should be evaluated probably with imaging and blood tests...I suggest a visit today to your doctor's office, Urgent Care, or the ER. Hope this helps:)