16 month old wakes multiple times a night no matter what we do

My 16 month old son has had a really hard time sleeping since birth. We are now at the stage where we want him to sleep independently, through the night, without waking up. However, it never happens.

He does not like pacifiers, and does not need feedings at night anymore. We have tried both with and without white noice sound machines and night lights. Even if we co-sleep (which we have done a lot), he still wakes up crying every two hours or so, sitting up, tossing around and seeming distressed, before going back to sleep. He doesn’t want to be held, and we just have to wait it out for a few minutes.

Could it be a medical issue? Or nightmares? How do i find out what’s wrong, and what can i do to help him? 🥺