My LO IS 4 mo (19weeks) and right from beginning hates tummy time...
He screams,gets congested,dosen't hold his head up....he makes such a fuss that I have no option but pick him up...
The main problem is he is able to roll from back to front and then gets stuck..I've tried toys/books/mirror/me in front of him but nothing works.Other things seems to be OK,as he sits(supported),holds his head ,supports his body on his legs really well,so why he hates being on his tummy so much? 
I'm a bit worried about milestones....my other 2 were OK and started walking fairly early(10 mo and 8.5mo),were crawling and enjoyng tummy time since day one and this one seems to be a bit on a lazy side...
Should I panic or just let it go....????