The ego is a projection of your "ideal self" that acts as an interface with the outside world.
It is a mask, a construct you built over the years, and when I say "ideal" is a delusion, because we suck at creating our masks, for they are a projection of all our insecurities ending up as a fake persona that we want to be identified with to farm validation from others and feel accepted.
But you can’t be seen for who you truly are when you present the mask. So no matter the validation, it’s temporary and fade’s because you can’t feel accepted when your true self is hidden behind the ego.
This is the dissonance you feel. In time we get used to our ego as our avatar because it is the one who gets validated by others and because "nobody will really like the true me" is a very common insecurity we often develop during childhood and coming of age.
So the ego is what stays often at the wheel, often steering us towards true trash decisions, is the one at the wheel when people cheat. If it wasn’t the ego instead of the true self of the person, they wouldn’t have any shame, they would not lie, they would be promiscuous but unapologetically so, they would not cheat they would declare they want multiple partners, take it or leave it.
The ego lies, cheats and betray because you are feeling shame for the hurt you cause to the other person, unless you are a psychopath, but the ego can play the psychopath role without you feeling like one, because you know is not the real you, is just a mask for the act, so it can give you the thrill without you feeling like a bastard as "this is not really me, who I am" after all.
It’s complex and nuanced but in a nutshell this gives you the general idea.
Look, sex is not the intercourse. Sex is the whole thing, emotional and physical intimacy.
It is the manifestation of a connection.
When you act like roommates where occasionally there is intercourse, sex is likely broken, as in the connection is broken by some unresolved issue between you.
You are not friends, you are not roommates. Though you end up act like roommates/ friends with benefits that play the couple without allowing themselves to embrace being a couple.
This is what I mean when I say there is some unspoken unresolved issue that you both need and probably want (but are scared) to address.
And the issue might not be functional, there can be some fundamental unresolved issue that both of you need to heal to come back together into the connection that generates the sexual attraction and gravity.
It doesn’t mean that you have to be aware of, but your guts tell you both something is off.
Infidelity, that’s the atom bomb that ends love relationships.
It doesn’t solve, it only corrupts and destroy, but you know that already.
It doesn’t necessarily mean that you can’t possibly start fresh, it is possible if you are both healed and the betrayed can get over their trauma.
But it’s not easy.
And requires to fully healed people.
The bs heals the bs.
The WS heals the WS.
You have agency to heal yourself