My 6 month old still hates tummy time... She is such a happy baby until I put her on her tummy, then she's unsettled for ages. I have to admit that because of this, I don't do it every day. Perhaps once every other day. I know, terrible 
Health visitor believes that she hates it so much because she is refluxy.
She does love sitting up however, and I try to have her sitting on my knee a lot. Her head and torso control seem to be on track. Am I a terrible mum?? And what can I do to help her with tummy time?