Nap Struggles

My LO will be 4 months next Thursday and for the past week, naps have been a major struggle. I feel like I have a newborn all over again. He cries and fights and it takes forever to get him to sleep. Then he only sleeps for 20-30 minutes before he's up again. He goes to sleep by himself at night, and still sleeps fine, it's just naps that are the problem. He's never been a great napper, but we at least had gotten into a groove. He's a happy guy all day and a really chill baby, until I try to put him down for a nap. I'm also struggling because he is starting daycare on August 29th, and they don't allow anything in the crib, not even a sleep sack. He's been sleeping without anything for a few weeks and doing fine, until this past week. After a long struggle this morning, I broke down and swaddled him. He still cried and fought a little bit. I got him calmed down, put him in his crib, and he fell asleep. Is it a mistake to start swaddling him again only to have to break him of it all over again? I'm pulling my hair out over here. I don't know what to do. I also think he may be transitioning to 3 naps and longer wake time, but I don't know. Help!