Do you force it?

DS is 3 months and up until a month ago liked tummy time. Now he snorts, slobbers, and SCREAMS during tummy time. He lifts his head, etc and actually kicks and manages to spin his body in a circle but hasn't rolled over yet. Am I just torturing him by making him do it every day? I do it probably 3 times a day and let him go until he is ballistic (which is usually no more than 3 minutes....)