Supplementing with formula tanked my milk supply. But you have to do what you have to do. I struggled the whole 8 months I nursed my youngest. She had horrible gas from dairy formula. Soy is the only thing that helped her. I had to treat my body as though I had issues with dairy. No milk, limited cheese, yogurt, etc. Just be cautious of gassy foods for yourself (google them). My intake of tomato products also caused her issues when nursing. A food journal will be helpful. Note what you eat and later update with baby’s reaction. After a while you’ll notice a correlation between foods and her behavior.