I understand how you feel about giving up breast feeding. There are the "breast-is-best" women who will make you feel awful for feeding your child even a drop of formula, and then those who didn't even try to breast-feed who get defensive from the other side. But most of us fall somewhere in the middle.
You don't have to give up breast-feeding if you don't want to, even if your son isn't getting enough milk. I was forced to supplement my breast-feeding with formula from day one because of production issues, but I continued to breast-feed as long as I produced milk (about 6 months). Talk to your doctor or pediatrician about increasing your milk flow (there are supposedly ways to do it, although none worked for me), but until that happens (or in case it doesn't), feed your son from the breast until it is empty/he gets fussy when eating. Then feed him formula in a bottle. This way, he always gets breast milk when he is hungriest and drinks as much as he can, but if he is still hungry after you're done, he can fill the rest of his tummy with formula. I think you'll find that he'll sleep better as long as his tummy is full.
Increase how often you pump and drink a lot of water. When giving him the bottle of milk you have pumped, once again, give him the milk first and if he finishes a full bottle, then give him the formula (you can mix it in the same bottle). Every single drop of breast milk is like liquid gold, so even if you can't exclusively breastfeed your baby, or even if breast milk doesn't make up most of his diet, try to keep as much breastmilk in his diet as possible. This method will help you save money on formula and know that your child is getting all the breast-milk you are producing, plus a little extra. It's hard work, but knowing your child is getting enough to eat will help with the stress you're feeling. Having formula to fall back on helped me to relax about breast feeding and know that I was doing the best I could, and I was still giving my son all those good anti-bodies. Good luck.