Pecan and 1ofmany, I myself do not like being penetrated in the ways one would normally imagine. And I haven't had sex with a guy since I was a kid, like when I was under 20. I can't imagine it would feel good to be penetrated vaginally if you were constipated. But, maybe some folks do like it.
I recall one time I had a lover who liked being vaginally fisted. Before I do that I always put my fingers in there(her vag) first. I could tell she had to go and I asked about it and it was like she hadn't thought about it, but she said yes, she had gotten constipated bc she'd been travelling.
That might have been the first time I mentioned enemas to her. She didn't know what they were! I said I didn't want to fist her if she was constipated and at first her feelings got hurt bc she *mistakenly* thought it grossed me out. I told her she was wrong, that it didn't gross me out, that I didn't care, but that there wouldn't be enough room and it wouldn't feel very good probably. She was small and had never had sex with a dude.
I didn't fist her that night and once I answered all her questions about getting an enema she was down with it and started requesting them often. We don't sleep together anymore, but she still mentions them occasionally, in a wistful, missing them sort of way. She'd say something like "I'm not empty enough for you to fist me. Maybe you should give me an enema first."
I knew another woman who really liked having sex when she had a full bladder. Something about having to pee made her orgasms more intense she said.