the peeing sensation is natural, i mean if you're really nervous about like peeing the bed or something silly, then try getting yourself off in the bathtub, or put a towel under you, then that might ease any worry you'll have about making any sort of mess?
A lot of women's mental blocks are caused because they're afraid of someone watching them, or just of really letting go. I had a huge block for the longest time because i'm a very vocal person, but for the first year that i was sexually active, we could only ever get our groove on when it was in the wee hours of the night and everyone was sleeping and we'd snuck over to the other's place. *shrugs* We were too busy worrying about being caught than enjoying ourselves. Once we had some time to ourselves, then wahoo, it was great!
Best of luck again!