Mom and my Erection

I came home for Christmas vacation from my first year of college with a rash in my buttcrack. It wasn't horrible, but it had me itching. My mom noticed. She happens to be a dermatologist, so how perfect is that? Except, I was rather timid about telling her about it, because, well, it was in such a personal place. But what could I do except admit the truth? Plus, it did have to be treated. So, in her bedroom, I took off my pants and showed her. I was very embarrassed about her seeing my penis and all that. The last time she saw me naked was so far back I don't remember. Now, I was a hairy monster, or so I imagined myself in the circumstance. She had me lay face down on the bed and she spread my ass cheeks apart with her hand. My, that felt nice! I immediately realized I shouldn't feel that way about it. It was just my mom looking at a rash, after all. She let go, and went into the kitchen where she came out with a little bottle of something. She then spread my ass cheeks again, and put some kind of oily substance on the rash. It felt cool, almost cold. She spread it around pretty good. In the process, her fingertips brushed directly over my asshole a couple of times. I don't know what she was thinking. Probably nothing - just another patient with a dermatological situation, except this was her son, no big deal. But what was I thinking? I don't really know. Maybe it was just the gentle, greasy touch in such an intimate place, but I immediately threw an erection. I hoped she didn't notice with me laying face down on the bed. I had to readjust as my body was compressing the erection, and that didn't feel so good. Again, I hoped she didn't notice my movement, or at least I hoped she didn't know why I wiggled like that. "Oh, my boy's getting a boner!" she sang out, in a teasing voice. I guess she noticed. "Lemme see." "Hell no, Mom." "Come on, it's not like I haven't seen your willie before." "But not erect!" I couldn't even believe I had said that word, 'erect' to my mother. "I'll bet it's cute." "Geez Mom, just think of me as a patient." "They get erections sometimes." "Mom!" "Lemme see." I don't disobey my mother. So, even though I'm sure I was red in the cheeks, and felt like I'd rahter die, I flipped over on the bed, letting her see my rock-hard erection. "Why, that's beautiful. Maybe even better than your father's." She actually reached out and touched it! And, OK, I'll admit it, that felt terribly good! She then manipulated my scrotum, I guess looking for more of the rash. She then pulled my foreskin down for a moment with her fingertips, then flipped it back up over my bulging cockhead. I started to feel an inevitable orgasm building up. I was thinking that cumming with my mother manipulating my penis just couldn't happen. I'd certainly be guilty of something. The exact details, I couldn't describe at the time, but I knew I absolutely couldn't cum. I needn't have worried. A few seconds later, she said, "OK, put your pants back on Buster." Nothing more ever happened, and neither of us ever mentioned that evening. But I have to tell you I have masturbated to orgasm many times recalling that evening in my mind.