Supply when dairy and soy free

L

My son was getting really bad diarrhea and losing weight on my breastmilk so my ped recommended soy and dairy free formula. He’s way better! But I cut dairy and soy to be able to breastfeed again in 2-3 weeks, and now my supply is dwindling fast! I pump every 4 ish hours, but I can’t eat many carbs due to giving up soy (including lactation cookies!) and I feel like that’s ruining my supply. Help! What can I do?