Hey Michele -
I had a similar experience with my baby, though it was earlier. Does he seem to settle after the formula? Generally, consistent crying is a cue for either unsatieted hunger or discomfort. Is the crying in sharp screams, or whimpers? The sharp cries tend to be hunger. It's possible that something happened to your supply, and he's not getting enough to eat. If you're noticing symptoms fo a diminshed supply, its a pretty good guess. The fenugreek tea is helpful, but the increase in supply isn't really significant (despite the labelling claims). Have you seen a lactation consultant? They're infinitely helpful in trying to figure out what's going on.
Do you have a baby scale at home? Try weighing him before and after a BF session so that you can see how much he's getting in. You may find he's not getting enough. Have you checked his suck? Dip your finger in milk or formula - when he's hungry, he should suck your finger hard enough that you have a lot of trouble pulling it out of his mouth, and you should feel his tongue curl around your finger, and move back and forth between your finger and his lower lip.
There's nothing wrong with supplementing - don't let anyone try to tell you there is. I had a lot of problems breast feeding because my baby was given a bottle (against my wishes) in the nursery during my C-s recovery. It was a nightmare - finger-feedings, reteaching her to latch, screaming baby, ugh.
In the meantime, my mother and MIL both basically made me feel like I was a horrible person for not having instantly abundant milk, and for supplementing her rather than just "letting her nurse" 24/7....the fact that she couldn't latch was also somehow my fault. I drove myself crazy for about 4 weeks, and finally just gave the baby formula in a haberman feeder. Since then, she's been the happiest, easiest baby I've ever seen.
It also may just be a growth spurt, and he needs more than you can produce. Try supplementing him after each BF session and see how much he takes. At around 9 weeks, my LO was hungry 24-7!! Her intake of both BM and formula increased dramatically!
Anyway (and I'm not saying this to scare you, just something to be aware of) if he's rejecting the breast, I might also go see my OB/GYN to check my breast. In rare cases, babies will reject a breast due to an as-yet undetected malignancy. It's almost certainly not the case, but it does happen. Again, if you're noticing a drop in production, its something that needs to be assessed.
Also, I would probably seek a second opinion, or be a little more aggressive if my pediatrician was so dismissive. Colic is not a blanket excuse for a crying baby. If my ped flatly told me that it was colic, with your description of the situation, I may find a new ped....
Good luck, and try to hang in there!
~O.