Need advice

Ladies, our 3 month old wakes up every 20-30 minutes for both naps and nighttime sleep. This has been going on for several weeks. He only sleeps if we hold him. Otherwise he just startles over and over again or wakes up to be held and comfort nurse. My hubby and I are past exhaustion. I spend a big portion of my day in a dark room holding baby so he will sleep. I stay up until 3am every single night. No joke. We are sleeping in separate rooms at this point so we can each get some sleep. It’s lonely and isolating. Hubby takes him from 3-7am and that is my only 4 hours to sleep. I’m awake for 20 hours straight every single day. It is wrecking havoc on my health. I feel horrible about myself because I’m not able to lose the baby weight. I walk around in a total brain fog all day. I’m so sick of playing on my phone to stay awake I could puke. Please help - how can I get baby to sleep longer than 20-30 min without waking up? Please no CIO. That isn’t a solution for our family. And no bedsharing, I’m too scared to do that. We want a healthy and safe solution to just get maybe a few more hours of sleep. LO does not have colic, and is gaining weight fine...only issue is constant waking to be held. Once held, he sleeps several hours. But we don’t sleep if holding him for fear of not being safe. I go back to work in a week and am terrified of this never getting better and being this sleep deprived on top of full time work and being Mommy. I love holding LO...but have to get some sleep! Thank you!