Little embarassing things happen. Most of the time, I think the gals have seen it all.
At my last session I came quite early into my 30 minute time slot. She laughed, but not in a mean way. Other times I got stage fright, or pre-gamed too recently and struggled to finish at all.
Unless you go all the time, or have some other complication, I would definately save play time for my day off. It's so much nicer to get ready for this kind of service.
Even make a day of it and hit the gym, sauna, and steamroom after.