Full Body Orgas[M] with [F]WB

I'm seeing this cute girl named Nicole. She's 5'6", plays volleyball, and is very open about her interests in bed. Typically, I'm more reserved when it comes to letting my kinks out but she is so casual with the whole relationship that I find myself telling her things I would only consider telling a long term girlfriend. She's been to a few S+M club meetings and she says they focus communication as being the key to good sex. What's relevant here is that normally I don't tell girls about my sensitive back because I'm still trying to figure it out myself; but, with her, I told her the first night I slept with her. Nicole was understanding and then began trying different things to see what it did to me. She giggled a lot (only adding to the sexiness) because I started to lose control of my body when she got the right pattern down. It feels really good! Almost like an orgasm, but not quite. Like I said, still trying to figure it out.