Breastfeeding and desperate!

I have been trying to up my supply b/c my baby gets fussy at every feeding after a while, like there is no more milk coming out or something...and also I want to stock milk but I haven't been able to produce more, even tho I eat 3 meals/day and drink plenty water, tried pumping, hand expressing (which seems to work a little better than the electric pump), compressions, hot showers, tea drinking, eating oats and what not....I still barely express 50 ml at best, from both breasts and after a good 30 min of hand expressing

I should mention that my LO weighed 3.4 kg at birth (sorry but I am not familiar with the imperial system) and now he's almost doubled his birth weight, at 3 and a half months. The pediatrician says he is growing really well and his latch is good and all, but he gets so fussy after just a few minutes of nursing (he was feeding very well for the first month, the fussiness started after that) and I try to switch breasts every time he does that, and then switch back and forth until he doesn't want to latch at all, and when I give up and lift him up on my shoulder for burping, he starts crying harder like he knows the nursing session is over but he wants more....

Also, since 1 and a half months he has been pooping only every week or so (6,7,8 days in between)

Can anyone relate? I really need help...

Sorry for the long post