Breastfeeding and weight gain

I have been having issues with my supply (as confirmed with a LC), so I am drinking low sugar Body armor, eating a bag of lactation cookies, and eating quite a bit of oatmeal and it has been helping. However, now I am gaining weight and overall, don’t feel well in general. I will do whatever it takes to continue breastfeeding, but I am a little worried about my health as well. I tried adding a bunch of vegetables and cutting some of the sugary extras (lactation cookies) and my supply tanked. Any suggestion of what I can do to maintain supply and not pack on weight?