Totatlly normal. It takes about 12 weeks to establish your supply. It's around now that you don't 'feel' as full, but that doesn't mean your supply has gone down or anything. I pump, so I always know what I have... there are times I don't feel full at all, and I'm afraid I won't have anything to pump - but it's always the same amount. He's right around the age for a growth spurt to, which is probably why he's wanting to nurse more.
Fenugreek works well for most people. The trick is to take enough so that your sweat/urine smell like maple syrup. (I was taking about 3 pills 3 times a day.) You can also add blessed thistle to the mix... fenugreek and blessed thistle work best when used together. I took 3 BT 3 times a day also.