My boyfriend did something disgusting?

[RapStarActor]

Why he isn't he saying this stuff to you his gf ? it is a lot easier to get in the shower with somebody you are already with.
Only you can answer that, if He said that to you would you flip out or want to do it, because obviously whether it with you or not He wants it.
I'm willing to bet it is more about 'the act' of showering with a Girl is what he wants than this one particular Girl. For example a guy that wants a threesome, its very little to do with any particular female involved in the threesome think of it as an ego thing and a bragging to Friends things than the actual women involved.
Maybe He see's you as someone that won't give Him that fantasy let's call it, so he looks elsewhere.
Guys cheat for sex, feelings have nothing to do with it, at all most of the time.
Sounds like he is getting feelings of excitement from texting her, still don't know why he's not doing this with you. Maybe he's scared to ask you OR its a fantasy that will stay fantasy.

[Di Li]

Dump, run, and don't look back. Forgiving him so easily would be a sign of weakness, and if he is a manipulator, you're going to be a very miserable person. I think you should learn to do two things:

1. Learn to be mean
2. Learn to not forgive
3. Learn to be more independent (even if you are in a relationship)

If you learn these three things, you wouldn't even be in this predicament. Why are you even concerned for him so much? How do you know it isn't an act? But what I find most disturbing is this: why do you not want space?