You say DH wants another baby. Do you? Not all babies are the same. My DD was a lot more difficult than my DS. So if you do, don't let your son put you off. Your next baby could be a breeze. But if you don't want another, don't let him talk you into it either. I don't think that would be healthy for you.
I would bet money that when you need to go somewhere, you get more anxious about him having a sleep, he picks up on that and so won't sleep and it's just a vicious cycle. I don't think anything is going to change for you until you're willing to deal with your health issues.
I don't have any experience with anxiety, but I've seen some of your posts and do hope you're finally seeing someone about it. I think if you had that under control, you would find everything so much easier.
I know you probably just come here to vent, lots of us do. But do you realise that all your posts are negative? Even when something good happens like your DS finally eating, you turned that into a negative when you should have been ecstatic he was eating! Lots of people have given you advice about your anxiety and to try to help you deal with your DS, but you don't seem willing to take it on board. It can't be easy living like that and feeling so down and negative all the time which is why I hope you're getting some treatment for your anxiety. I know it must be hard to take that step, but I think if you do, things will get easier for you.