Hi A.,
Just keep breastfeeding for as long as you can. If he is not gaining weight like he should then you will need to supplement. It is no reflection on you as a parent if you end up supplementing a bit. Don't let hardcore breastfeeding enthusiasts tell you not to supplement now matter what if you end up needing to.
I breastfed both of my girls, but my milk dried up after a couple of months with each one. With my oldest, I was determined not to give up, and even though the quality of milk seemed fine at first, she, too, was sucking on her fist and crying after an hour/hour and a half. I was told by several not to give up and not to supplement, that eventually more milk would come in. It didn't. You may be different, so keep trying, but don't be discouraged if your little boy needs a little bit more than what you can give him.
I also began pumping more milk in between feedings to stimulate my body to produce more, but I couldn't get large quantities in the bottle because I was breastfeeding her so often. Then I tried going longer between her feedings so that my milk would build up, but the poor thing was ravenous and would go through the little bit I had pumped earlier in a flash. It was frustrating for me and I was so tired.
Once I began supplementing with formula, she let me know how much she appreciated it, and consumed more formula than I had ever produced with my breasts! Unfortunately, she began to prefer the bottle to my breast once she realized that more was coming from that area.
With my second, my milk supply was of a higher quality for a longer period of time, and she didn't cry between feedings like my first one. But, eventually, the supply also ran out, and my milk became a bit bluish-tinted - a sign of thin milk.
I believe that lack of sleep/stress from feeding so often perpetuates the problem. I tried the teas and did everything they said to do. But what it all came down to for me was that I was stressed out because I wanted to nurse 100% (with no formula) and I wanted to be successful at it.
Looking back, I did the best I could, and I should have been at peace with that instead of putting so much pressure on myself. I was much more relaxed with my second, which is why, I believe, I had more milk. I also was getting more sleep with her because she was a sleeper and could sleep for 4 hours when she was a newborn between feedings.
I will say a prayer for you - may God give you peace and many blessings for you and your family!