i actually had something like this happen to me when i tried (2nd time) anal with my bf. he went in but not all the way. he said he managed to get the head in then it hurt so i told him to pull it out. then after that i saw a drop of something brown on the sheets. at first i thought it was blood but i looked at it closely and it was like light brown in color. when i went to pee there was also a bit of brown discharge on my underwear but it just lasted within that day. were u wet enough when he penetrated u? and did it hurt? cuz when it hurts i tell my bf to pull it out right away
I've had this happen when I didn't clean out right and was younger. I attribute it to cum combining with errr some liquid in there, which then slowly oozes out, which explains why it can be on your panties the next day, and the bed that night - it's coming out as he comes out, etc.
Well I wont disclose my embarassing moment with this, but I'd go with the enema suggestion and see if that helps. If it's still happening, talk to your heath care provider and see what he or she says. Good luck!
This really doesnt seem like that big of a deal. If Your sleeping together you shouldnt be embarrassed about these things, and if he wants to do anal he should expect this kind of thing. If he really was mad about it, hes a douche. and you shouldnt be sleeping with a douche.