Discouraged

I never had a problem breastfeeding my first. Now this second baby seems unsatisfied all the time. My sisters milk dried up so she's constantly telling me my baby needs formula. My mom makes comments about how hungry he must be all the time. So a few days ago I started supplementing with three bottles of formula a day and the rest is breastmilk. I feel like a failure. The worst part is I'm not even sure it's helping. I think he's just a needy baby. He'll be four months on the 11th.