I haven't had sex on Mushrooms. But I have on a close analogue of 4-ho-dmt.
Sex on 4-ho-det was mind blowing. It was truly a cosmic orgasm that felt cleansing and awe inspiring. Orgasm was not possible at the peak. However about 20 minutes after the peak orgasm was possible. It was ecstasy beyond the ego. The visual representation of the orgasm brought together concepts of the self and reproduction that goes beyond lingual expression.
Its an exprience you share with your partner only a few times. Perhaps once a year, perhaps even less. It will take weeks to attempt to integrate and express the experience beheld.
I wish you all the best in your adventures lovemuffin. I am sure they will prove to be fruitful.
Sex on psychedelics is different to level headed intimacy, its more of a mind blowing experience you can use to shift your thoughts in a new direction. Especially if you expect change(any kind) in the comming days/weeks. Whereas non-intoxicated intimacy is purely more fun, without the weight of intense and sometimes overwhelming emotion.
Oh and don't forget to have fun!
*hugs*
-> WussPunkSUX : Can't get it up.
I know what you mean. We had a game for this... She would try to make me erect and we would see how long it would take... It didn't take long normally to get it up if she was interested in doing so, boy did it feel good. Bwhahahah.

Once it was up, traversing my thoughts to the point orgasm was a different challenge. Focusing on the pleasure centers, visualising archtypal imagery also helped. It isn't easy but once you get there, its hard to beat.