4 month old progress

I’m getting a little concerned. My son occasionally gets lucky and rolls over (stomach to back or back to stomach) but shows no signs other than rolling on his side from his back for rolling over. My son actually moves in circles instead of rolling. When doing tummy time he doesn’t hold himself on his elbows (he also hates tummy time). I feel like he’s behind, I’m not sure, but I’m definitely worried. He does great in his frog that helps him sit, he holds his head perfectly. What else can we try? I do a boppy pillow with a regular pillow behind him but all he does is scoot down. His next appointment is in two weeks if that matters.