Hi - you won't have to give up breastfeeding if you are willing to try going on a diet that is cow dairy-free. I had similar problems with my son when he was younger (he is 5 years old now and still drinks goats milk, etc.). I'm not sure if the cow dairy is your son's problem but it is always worth a try. Even if you give it up for a week only just to try, you should start seeing an improvement pretty quickly. We saw a difference in my son after only 2-3 days of being cow dairy-free. There are alot of dairy-free alternatives out there these days. I was a real cow dairy lover and I have to say that I never thought I'd be able to give it up but I did. We use pasturized goats milk as our main milk (doesn't taste as strong as raw goats milk but probably not as good as the raw stuff) and goats and sheeps cheeses. A good, hard sheeps' cheese tastes nearly identical to cow cheddar cheese. I use olive oil instead of butter in a lot of things like mashed potatoes, garlic bread, etc. And for recipes that call for butter I try the soy or safflower, organic, GMO-free "non-dairy" spread. I also use this on their sandwiches instead of butter or sometimes I use a goat cheese spread. The sooner you try these alternatives the better because if they work, your son will get used to eating them and they will taste fine to him. There are also loads of foods that are dairy-free, from cookies to crackers to even chocolate chips--you may have to shop at a couple of places to find good choices (like health food stores, etc.) but if it works it is worth it!
I occasionally eat cow dairy now that I'm not breastfeeding, but actually I feel alot better when I keep it to a minimum. We all have way less colds (due to less phlegm) and overall we feel healthier when we eat less cow dairy.
Good luck!!
Shirl Harrington
Beara Penninsula, Ireland