Exclusively breastfed baby gained only 1 lbs from 2 months to 3 months old. do i need to supplement? i gave him formula once and he guzzled 5oz...

Probably: It sounds like you are not producing adequate milk. Several measures can increase your milk supply. See http://www.breastfeedingbasics.com/articles/increasing-your-milk-supply & http://www.breastfeeding-problems.com/galactagogues.html Try those measures but you can also supplement with organic formula after nursing. See http://foodbabe.com/2013/05/28/how-to-find-the-safest-organic-infant-formula/

Probably not: Generally we look for babies to gain 1 oz/day, or 2 lbs. over 1 month. But saying that, each child gains weight at their own rate, and if a child is happy and active, then the growth that is occurring is what is intended. If there is any concern, that the growth has dramatically slowed, or you feel that your milk supply has dwindled, you should consult your baby's doctor

A lactation consult-: ant can help you try a Supplemental Nursing System. As I'm sure you know, your anxiety can work against you in this life situation, as in many others. I hope you have a supportive counselor & that your pediatrician has determined that your baby is otherwise physically & developmentally healthy. Your emotional availability to your baby is what's important, whether using breast or bottle.