TMI BUT HELP

So me and my boyfriend ( have been dating for a year ) were having sex on the couch, and I felt constipated but didn't really think anything of it and then after banging on the couch in the same position ( he was on top ) there was shit on the couch, it was from me but why would that happen, it wasn't anal. I felt really embarrassed and don't know if I can look at him without feeling embarrassed. It happened lastnight and I'm still thinking about it , someone please give me advice