Switching to formula??

My daughter is five months old and even with me taking prescription medication and a ton of herbs, I still don’t have enough supply to keep on breast feeding her. I’ve tried pumping every hour and power pumping ( I spent tons of money on a expensive pump ), taking medication that makes me feel crappy and she still has poor weight gain. I’m close to giving up. Did any of you ladies have the same issue and how did you feel about it?? I honestly have been trying only to feel like a failure of a mom because I am not able to breastfeed her for as long as I would have liked to. :(