Sleep training saved my life, well and truly. I was so tired I nearly crashed the car, and was also having dark thoughts. DH and I were snappy with other and it made me resent being a Mum. Cosleeping made little to no difference, and usually made it worse.
DD was either up every 45mins and needed a complicated rocking routine that only I could do (she'd just scream at DH), then I'd get maybe 25mins before she woke up again, OR she'd only wake once but it'd be for hours and hours. We were all miserable, including her. It was horrendous. So we did sleep training at 14mo and she slept through the first night. It took about 3 days for her to stop shouting when we left the room (1min intervals, never got over 5mins) and then after that she would chat herself to sleep once we said goodnight. We had a lovely, calm, consistent bedtime routine with stories and a song etc, but the sleep training was a miracle. She woke up happy for the first time ever!
DS didn't wake as frequently, but when he did he would scream, headbutt my shoulder, pull my hair, scratch me - pretty much from birth. These were all while I was rocking or cuddling or whatever. And he was SO heavy and strong, it was awful. I was at breaking point by 8mo and it was starting to affect DD (she was 4 and when he was really shouting it disturbed her too), so at 9mo we did sleep training with him. Same thing, a few days and he was sleeping through with no problems. He was still in our room at that point so I know there was no "not bothering to cry because nobody comes". He was content. If he woke, he rolled over and went back to sleep. If he cried, I'd give him a pat and he'd calm down and go back to sleep.
(This was all after they stopped wanting milk in the night - I'd offer them a bottle and they'd refuse so we knew they weren't hungry!)
DC are 11 and 7 now and sleep like champs. And if either of them do wake up in the night and can't get back to sleep for whatever reason, guess what they do? They call out for us, the horrible parents who did sleep training with them. They don't lay in the dark and sob, they ask us to come in to them, and we do. They also don't wake up screaming every 45 fucking minutes and make me want to throw myself off the roof, then be miserable all day because they're exhausted!
Sorry this is so long but it really was the best thing we ever did and I wish we'd done it earlier with DD. We had to redo it every now and then for illness and teething when they'd come in with us (we're not monsters, despite what some people will think!) but overall it changed everything.
It doesn't work for everyone but if it does work then it can change your whole family's lives. Nobody does sleep training to be cruel, they do it because they're at the end of their tether and can't cope with no sleep anymore.
Good luck, OP. I hope you get it sorted, one way or another!