Found out he's a compulsive liar - salvageable?

Today I found out my partner DX has been compulsively lying over who he is and also stupid small things, for the whole of our 5 years together. I strongly believe this is due to his really extreme RSD.

I knew he was lying and there was evidence of it for years but he convinced me I was paranoid and mentally ill, even encouraging me to go on anti depressants for it. Which I did.

Even tonight, after a day of devastation, I said "why don't you go on your switch" and he impulsively told me he didn't know where it was, even though he does! He admitted it was a lie and he didn't even know why he said it.

I've just realised that this man has lied non stop for our whole relationship and I'd love to hear experiences of others to calculate if this is salvageable.

Thank you