To be hurt he doesn't want sex anymore?

[maybebluth]

My DP has chronic illness, and hence we never have sex. I think it's partly because he's in pain or tired but also because he's a bit depressed and doesn't enjoy anything. I have found myself feeling like it's something wrong with me.

I would not normally read into it, but he had an affair four years ago so this is triggering old insecurities than I am faulty somehow...

Is the illness and the stopping of sex a recent thing? As that with the depression can easily answer why he is not thinking of sex with you, so not your fault or because of you, which can be heard to take anyway.
Can understand why it is a trigger for you, but does sound like it's the illness and the depression that is causing this lack of sex. I have had depression so can understand that the interest in things does drop off quite easily