guilty for formula

Does anyone else deal with guilt over using formula? I breast fed my daughter for about 6 weeks and now she's 7.5 months and lately I've been having times where I feel so deeply guilty for giving up on breastfeeding. It's weird because I know my daughter is healthy, she hasn't even had a fever yet, she's getting ready to walk, but I still feel so down on myself sometimes like I failed as a mom or something. It makes me not want to have another baby ever because if I breast feed the next one I'll feel guilty for not breast feeding my first and if I don't breast feed the next baby I'll feel guilty about that too. This is seriously consuming me. I'm also dealing with some post partum depression which might be playing a roll in the intensity of this guilt im dealing with.