If we are talking about milk, being breatmilk only, then I would give him PB8 to settle his stomach and he'll be back on the breast. Open the capsule and dump 1/4 of the capsule into his mouth before each feeding. It sounds like his tummy is upset, maybe some leftover bacterial growth than can be cleared out, often with a GOOD probiotic like PB8.
I find that ear infections are related to candida overgrowth, so I use PB8, vitamin A&D together, as well as Herbs for Kids Echinacea/Goldenroot drops. That's why giving a child/baby antibiotics increases the risk of ANOTHER ear infection by 33%, according to medical research.
You may want to consider stopping dairy and sugar, if you are eating that...and maybe start the PB8 yourself.
The ONLY time my oldest got an ear infection was when we allowed yogurt and some cheese. Generally, kids who don't eat dairy or sugar never have ear infections. My kids do neither and are NEVER sick. I think 3 years ago, my oldest got a slight runny nose for 2 days and that was it. Other than that, they've really never been sick. we've never given our 3 younger ones yogurt or really another other dairy, but the occasional cheese.