Why is my baby crying so darn much?

My baby will be 17 weeks old tomorrow, shouldn't her colic be gone by now?? On top of being a high need baby, she cries/fusses CONSTANTLY. She doesn't spit up but I've noticed she won't drink more than 4 oz at a time sometimes less. I understand that her temperament could be the reason for some of the crying, as she gets frustrated very easily when playing with toys and is very picky about the way she's held, fed, etc. Of course if I hurt all the time I would be too. I've tried everything from elevating the head of her bed, exclusively nursing (with drastic changes to my diet over and over), formula feeding only on several brands/types, herbal teas (they do work to a certain point) solid foods, mage, taking her to a chiropractor (he said she was his toughest case, after 2 months I quit), ER visits, car rides, singing, swings, white noise, clic music, the "colic hold", probiotics, infant's tylenol, switching diapers and baby baths, and anything else except extensive blood work or a X ray/MRI whatever. She's very big for her age, and chubby too. She weighs nearly 17 pounds and when she's in a good mood she's very agreeable and sociable. And she pees and poops really good, but I've noticed she seems to cry alot more when she's about to have a b.m. But I can't take her anywhere for fear she'll start crying!! AS far as wearing her in a sling, she is too heavy for that, doing the hip thing throws my back out of place (I'm smaller framed) What else could be wrong with her? Any other "colic club" patrons out there with some advice for a third time mom who's about to lose it?? (Hey at least she sleeps pretty good at night time now, but she won't nap more than 30 mins) I think it's GERD or a commonly over looked tight rectal opening, neither of which I could treat. I just want my baby to be happy!!