So the other day I was with my fwb and we were having a great time when suddenly we began engaging in an inter course session and all was going well until he asked me to flip over on all fours and "throw my ass back" in my head I'm thinking okay easy enough but when I tried to make my body actually do this position it was stuck. I was a little embarrassed because I couldn't "throw it back". He laughed it off and just took matters in his own hands but I can't stop thinking about it.  How do I get better and actually be able to throw my ass back and pleasure him just as well as he pleasures me? Please help I'm desperate to learn.