stop breastfeeding?chalenge with toddler

how do you breastfeed with a todller wanting your atebtion?zi alredy dont have enough milk supply so I have to give also formula for my baby...I know breastfeed is the best for him but i dont think I can do it anymore :( it is taking everything I have emotionnaly and physically I am not doing very good at all..How do I stop?anybody went through this?my baby is 3 weeks now and my toddler 2 and half