It's so hard. With my son, I would try to nurse him back to sleep and put him back in his crib in our room. I would do this over and over all night, and I would get so little sleep. And I couldn't fall asleep after he passed out. I lived in a depressed morass for 2.5 years until he finally took took to sleeping by himself (my
milk dried up because I was pregnant, and so I transitioned him to his bed. My memories of the time are super hazy as to exactly how I got him sleeping in his bed. I think I patted and sang him to sleep--which would take sometimes an hour or more). Of
course, because I got him sleeping through the night, this included sleeping so soundly that he wouldn't wake up to
pee. We dealt with bed wetting until he was 5, I think.
My daughter still sleeps in bed with me. She's four. I wasn't going to be (as) sleep deprived with her, so I just co-slept. She continued to wake up every 1.5 hours through the night until she was 3 1/2. But, she was night trained at like 2. And, since she was in bed with me, 90% of the time, I could stay sleepy when she'd wake up and need me. While my sleep wasn't perfect, it was better than with my son.
She's 4 now, and we're trying to get her to sleep in her own bed. It takes about an hour a night of sitting in there (I read a book with a dim light, to maintain my sanity) until both kids are asleep. And then she sleeps in there for about 3 hours, which is when I take her to my bed and co-sleep.
I don't think there's any perfect options for any of this. I sure haven't found them! But your sleep and sanity are super important, and I know mine was really breaking when I was going through what you are. It's HARD.
Oh, and I was also the kid that didn't sleep through the night until I was 3. And even then, it'd take me 2+ hours to fall asleep. My brain just couldn't shut off. I'd lay awake watching the moon, or counting the squares on my curtain, or praying, or recounting my memories or making up stories. I never wanted to be awake. I actually begged my mom once to bap me upside the head with a baseball bat so I could pass out. Bed time was 8:00pm, and I was often still awake until past 11:11pm. That's over 3 hours of laying in bed, staring at my clock, trying desperately to pass out.
Some things that help me sleep better now, is having white noise, and also black out curtains. I need it to be DARK. If there's light, it has to be red light, to help my body know it's bedtime.