Could this be because of the dairy in my diet?
Probably not. Almost all mothers can eat anything while breastfeeding. The symptoms you attributed to milk in your diet may or may not have been from milk. It's normal for babies to spit up and have gas and your baby may have been in the normal range. It's normal for a baby to go a couple of days without a stool and then have a huge amount of stool. One of my sons would do this in the car seat and it would go out the diaper and clothes and into the car seat and I would have to put the car seat in the tub and shower it down and clean it. This happened on more than one occasion. Your baby didn't eat because she was uncomfortable because she was full of poop.
We are now realizing that reflux can be caused by the position the baby is in when they nurse. Somethng called laid back nursing may help prevent reflux. Reflux used to be rare 25 years ago. Breastfeeding has become more prescriptive. Mothers became more concerned about "proper" positioning, latch, and watching for everything to be just right. Reflux has now become the norm. The position mothers are now using may actually causing reflux. If you go to google and type in laid back nursing or laid back breastfeeding you can find a lot of info.
I doubt there is any reason to limit your diet unless you or your husband are allergic to milk. Lactose intollerance doesn't count. It is normal for people over 3 to be lactose intollerant.