You have every reason to feel this way, love. I've never gone through anything similar so I won't insult you by pretending to know how you feel, but please know that we're here for you every step of the way.
Your son is probably a little bit confused by the situation (why is mommy laying down all the time, why is she crying, etc) and might also be picking up on your feelings. He's still very young, so it doesn't surprise me that he's finding comfort from his father. He still loves you. Just give him some time to adjust, okay?
And allow yourself to feel sad, depressed, angry... Whatever's in there, let it come. You won't do yourself or your son any favors by holding it in. Any time you feel the need to let it out, you can always come here and rant. Try to keep the faith, and remember that your little boy is still safe inside your tummy. There are some things you can't control, but what you
can do is take care of his mother emotionally.
We're here for you.