My 6 month won’t sleep thru the night

Hi! Looking for some advice/support on sleeping schedules and nap times. I am trying everything to get him on a schedule of 8:30 am nap 12:30 pm nap and 4 pm nap in his crib but he just wants to sleep whenever wherever, sometimes for 20 minutes or less! Wakes up cranky and fussy within an hour to where I nurse him to sleep again. I believe it could be teething.. all day long I guess what is wrong why the fight and fuss.

Last night I tried for the first time transitioning him from my bed cosleeping to crib and he was up every 2 hours I barely slept. I know it probably takes time but I am afraid I am doing it wrong and he will not respond to soothing himself to sleep, I do not let him cry it out and I try to wait as long as possible before picking him up. He sleeps best in my arms, how do I break that habit without leaving him to cry and cry in a panic? How can I get him to nap on a schedule and sleep longer then 20-30 minutes?