Rolling

I feel like a crap mom. I try to give my son plenty of tummy time. With toys around him just out of reach, with his toy arch above him to look up, the piano that plays music and lights up, I’ve even played sensory videos and Ms. Rachel to keep him interested. He gets on average an hour a day. But he has zero desire to roll over. He was rolling tummy to back but hasn’t done so in a couple of weeks. I work with him daily using PT recommendations from YouTube. He appears to have all the ability to when motivated but seems to lack motivation and has zero desire to. Same with pushing up like a push up on his arms. He can do it if I prop a boppy or blanket under him and basically push his arms under him but he’s so mad about it. He will be six months on the 19th and I’m afraid he will be behind. 😭 he was this stubborn at 2 mos with tummy time and lifting his head. When should I start worrying? I’m already worrying but when is is appropriate to begin worrying about delays in rolling?