4 month throwing tantrum every nap

My 4 month old has started fighting every nap so hard, he starts crying as soon as I bring him in the room to nap and sometimes it takes an hour or two before I can get him to sleep (when I try to put him to nap after 1.5 hours of wake time) a couple times I've just had to give up and brought him back out to play but then of course he has a meltdown a little while later and I'm already totally exhausted from all of the crying. He goes to sleep beautifully at night, we bedshare and he wakes up during the night, and has been sleeping light and waking up a lot toward the later part of the night but he just nurses and goes back to sleep. He does wake up at 5am (and a couple times 4am) no matter what time I put him to bed, but usually he goes to sleep between 6 and 7:30 pm. Any suggestions? Is this part of the joy that is the 4 month changes and should I expect it to go back to normal? At first taking him for a walk would get him to sleep when rocking, nursing, etc wouldn't, but today that wouldn't work either. He doesn't self soothe and I'm not really sure how to teach him since we bedshare (and don't think I'm ready for that battle considering how exhausting nap time already has been even with comforting him with all the no-no sleep associations)