Sleep train?

My baby has never slept through the night since birth. The most he lasted was 4hrs when he was 2 months old. After that he would wake up at different intervals (can be 20 mins, 30 mins, 45 mins, 1 hr, 1.5hr, 2 hr, 3 hrs etc) He also sometimes wakes up too early (3/4am) and can't go back to sleep even though I've tried nursing or rocking him. It took us 2-3 hrs to get him to drowsy state. Now it's worsened cos he started rolling but can't roll back. We've been helping him nap/sleep either by rocking or nursing. He's never slept by himself before. I tried to sleep train recently using the gentle CIO method, by putting him on his cot awake. But he cries even before touching the bed, or stays alert all the way till he becomes bored or upset and cries. I tried to pat him but he just turned hysterical and became inconsolable after some time if I don't pick him up to calm him down. It will take my husband and I hours to calm him down. He's 4.5 months old now and it seems that he has the ability to self soothe (he will suck his hand or toy when he's abit fussy). We also have this bedtime routine where the lights are dimmed, I put on music and read a book to him. But it always ends up with him crying and I rocking him to sleep. I'm wondering if there's a gentler way to sleep train or if I don't sleep train will my baby learn to sleep without rocking soon?