This article describes symptoms of lactose overload and things you can do to help it:
Lactose Overload

This one discusses lactose intolerance.
Lactose Intolerance

I'm going to quote some of that article:



This article is written by an experienced IBCLC and ABA counsellor, with a Bachelor of Science in Nutrition, a post grap dip in diet and some other letters I don't understand, lol.

Seven Oaks, I'm really glad you guys found something that worked for you and your DD. But I urge anyone concerned about lactose allergies, intolerances or overloads to speak with a paediatrician with specialist breastfeeding knowledge, or an LC or other medical Breastfeeding specialist. The ABA is a great place to start.
Exactly the links I was going to post and with better surrounding words - cheers OP.