Feeding , milk?

Jez • Wife🤍 mommy X2 👶🏼🦖 + 👶🏼🎀

Hello! My son is 5 weeks and 1 day... I’m not really producing quite enough breast mills for his needs... I’ve tried multiple different formulas and mixed them with my breast milk and he gets quite upset with them. Gassy, constipated, etc..... would I be able to mix my breast milk with soy milk just to meet his needs a bit more or is there any other suggestions???