At the Physical Therapists

I recently had knee surgery, so I had to go to physical therapy 3 times a week. I picked a therapist that was female, and a quite attractive 30 years old. There was also a female receptionist/assistant in their small office. I would come over during my lunch break and change in behind a semi-private room. The therapy would last about 30 minutes, then they would ice my knee for 10 minutes. One time while they were icing my knee, I began to fantasize about having sex with the therapist. At the end I had quite a hard-on and I'm sure the assistant saw the bulge in my shorts when she came to take the ice off. I was instructed to go ahead and change back to my work clothes by hind the curtain. I was so horny though, I just started jerking off until I came on my shorts (that's all I had handy). As I finished dressing and left, the assistant flashed me a wicked smile and asked if I felt better. I blushed and mumbled yes and left.