Oh man, sounds like my son at that age. He started that nonsense around 4 months and by the time he was 6 months I was losing my mind. He would just scream if my husband tried to settle him, so it could only be me. All night. Every night. I'm sorry. I know how hard it is.
After speaking to our pediatrician, we decided to sleep train at 6.5 months. I was against it, but (1) I was losing my mind and (2) he was obviously not getting enough sleep--he had bags under his eyes and was grumpy and irritable. It was a mess. I knew I wouldn't be able to handle any amount of "controlled crying" so I stayed at my mom's house for a few nights while my husband did the hard work. He had been sleeping in our bed or in a pack n play in our room, but my husband transitioned him into his crib and did some "controlled crying." I was adamant he NEVER get left to just cry himself to exhaustion feeling abandoned. I'm told the first night he cried for about 15 minutes and then slept 10 hours. Yeah. TEN HOURS. The second and third night were actually worse, but never all that bad.
Despite how well it worked... it didn't stick. He'd get sick or go through a new developmental phase, and we'd be back to very disrupted sleep. I think there were two additional "sleep training" sessions my husband did while I stayed at my mom's between then and 18 months or so, and I said no more. It would work for a few months, then we'd have a few months of bad sleep, then he'd sleep train, and it'd work, then it wouldn't... I said forget it. No more. Especially as he was getting older I think it was worse for him emotionally to go through "sleep training". So, we just did whatever we could to make sleep happen (usually me on the floor outside his crib and then he'd come onto the floor with me at some point for the rest of the night). We were getting sleep, but it wasn't ideal. At like 20-22 months or something, he just started sleeping through. And he has every night since (except for the occasional cold or something).
I know how horribly hard it is on you and your baby at this point. Despite my long rambling, I really don't have advice. If it's really gotten to a point of suffering for either of you, try something different. But, also know that it's really common at this age and your baby WILL SLEEP THROUGH THE NIGHT (at some point).
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