It absolutely sounds like a symptom of the reflux. My daughter was at her peak in terms of how bad her reflux was at 4 months of age. We have only just managed to wean off meds successfully with her recently and she is 4 years of age.
Breast refusal with reflux happens because they develop pain association. I did not have much support with my daughter and ended up having to stop breastfeeding at 6.5 months due to the severe breast refusal that was just getting worse and worse till I was not in a good place mentally as I was so anxious about making sure she would feed ok, not be dehydrated etc. I got mastitis countless times and she started losing weight, stopped growing in length etc. Up until this point she was a frequent feeder (comfort feeder) and was a big baby who put on a lot of weight. Most reflux babies are at either end of the spectrum, they either are small or are big because they are feeding so often to try and soothe, but then they later (sounds like your son) work out what is hurting them.
I suggest that you get onto the doctor about managing the reflux better, as I was devastated to give up breastfeeding, but in the end really did not have any choice as it had gone on too long.

The Reflux Infant Support Association is a great organisation and offers lots of support. there are forums, a private facebook page for members to post and ask for advice etc, a library and lots more. I didnt join until both my refluxers were much older as I kept thinking they would grow out of it (which most do, but mine didn't) and wish I had joined much earlier for support and guidance. I am now a volunteer for them as an email contact among other things.

I don't want you to have to stop breastfeeding, as it was really quite soul destroying to me as a person at the time and I actually needed counselling to come to the decision to stop and be ok with it. If the reflux is sorted out soon, you should be able to continue your breastfeeding relationship. I just wish someone (including the docs at the time) helped me and supported me when I was having so much trouble with a baby who didn't want to feed.