R.A.
I think it's great to breastfeed, but if it's stressing you out, or you are unable to get your milk supply where you feel it is enough, don't beat yourself up about using a bottle. I breastfed all 3 of mine, and with my last, she went on strike for a few weeks, and I ended up just switching to formula. I was nervous about it, but it turned out that she started gaining weight, and she hasn't been sick. If you are dead set on nursing, then I would talk to a lactation consultant. I am pretty sure that there are ways to increase your milk supply. It will just take diligence on your part :) Good luck!