6 month old wont stop crying.

Hey ladies, my 6 month old wont stop crying and screaming at the top of his lungs. Ive tried everything, feeding him, changing his diaper, tried getting him down for a nap, tried playing, tried releasing gas, checked for hair tourniquets on all fingers, toes and private areas, gave him tylenol for his teeth, tried AC on and off, tried music/white noise on and off, tried going outside for a walk and to the park, tried a bath, tried rocking him to sleep, bouncing him, tried just putting him in his crib and NOTHING is working. Hes been screaming for almost 4 hours off and on and wont nap. I tried multiple times to get him to nap in the last 4 hours and he wont. Just screams and cries when i try. His pee is clear and doesnt smell and he isnt noticeably more upset while going so i dont think its a uti, he isnt pulling at his ears and otherwise seems well so i have no clue. Any ideas?