No decent sleep since August

My baby slept great until he hit the 4 month regression. He got so bad to the point that he refused to stay on his crib or PNP since he was 4 months old. (He is 7 mos now) The longest he would sleep on his PNP would be 4 hrs. Usually from midnight until he wakes up (7am), I would have to carry him. I would try multiple times to put him down again and he would just scream bloody murder. This has been going on for 3 months! After we noticed that the regression subsided, we realized he was on another leap--so I thought ok, few more days and he'll go back to normal. He did for a couple days then he got the cold (which he still have until now)

I literally have not slept on my back longer than 4 hrs since August. I have been carrying him to sleep since then. I am more than sleep deprived. I am working as a nurse, I am in school, my inlaws are sick and they are the only family we have, and my husband can only help during the weekend.

I have looked into sleep training and we actually did one right at 2 weeks old and he did great. I mentioned this ongoing problem with his doctor and she said I have to be patient because he doesn't feel good.

I don't care if I'm tired or have no time for myself but I am afraid my body is starting to crash. I have been having chest pain, which I am assuming is from stress and anxiety. Did I mention that my boy is over 22lbs at 7 months? Yes, he is freaking heavy.

I am beyond lost. I feel like a failure. I have tried everything you could possibly think of. I even tried the CIO method which I swore I wouldn't do and 15 mins in, he is still crying his lungs out.

Any other sleep training methods you would suggest? I honestly got no hope anymore but I'll keep trying :(