It sounds to me as if he really does love you but is trying to fight that "I'm not good enough for her" evil weevil and all the other negativity that depression throws at you.... Sweetheart I know it's hard - believe me I really, truly do and I'm not making excuses for him at all... but if you want to make this work then a lot of it comes down to patience and a lot of talking and even more listening.
I know that sounds like a really sh(t answer and isn't giving you an answer, but it's the best I've got and I've been with Marc for 19 years.... It isn't always this hard....