You do deserve better. He needs to be a big boy and accept that I'm can't have his fantasy of having you both.
You got comfortable and let the boundaries drop. Ok time to put them back up. Remind him how you feel about being friends with him while he is involved with OW.
I think I got one of those mistake texts once and it haunted me for weeks. I'm sorry.
Me 44 H 42 M 10 T 12 (at time of BD) Ss 20 16 S11 (special needs)
BD 9/13 H "unhappy for years" moves to seperate bedroom 10/13 EA/PA confirmed but denied S and I move out 3/15