Not rolling over

My daughter will be 4 months old on Saturday and she is not rolling over. She has done it maybe a handful of times but she absolutely hates tummy time. I will put her down for tummy time and within 2 minutes she is screaming and crying so loud. I really am lost. I've tired everything. No toys get her excited about it. I'm down on the ground trying to encourage her and nothing. She just screams and screams. And she also shoves her hands in her mouth and chokes herself and ends up throwing up. I'm seriously at a lose.