Exhausted from breastfeeding but feel bad about even thinking of putting him on formula

I never wanted to breastfeed, my son was born at 36 weeks so I decided it would be best to breastfeed him since he was a premie, I never got back on my depressing & anxiety medicine because I don’t want that in his system, even if the doctor says they are safe I just don’t want him exposed to it. I liked it at first but now I’m tired & need help. pumping is tiring & hurts my back & so does feeding him. Any position I’m comfortable in, it doesn’t work for him & he unlatches. I’ve tried EVERYTHING all the pillows & stuff to help support me but it doesn’t work my back is on fire, I’m soo tired & I need help. pumping is too time consuming but even the idea of switching him to formula makes me feel like a bad mom 😢 idk why I feel like this because while I was pregnant I was 100% sure I wasn’t going to breastfeed. I literally cry just thinking about switching him to formula.. I’m scared I’m going to regret it. I just need help making the decision I guess. Maybe even some reassurance that I’m not a bad mom. I just need help. He’ll be two weeks old on Tuesday..

EDIT: thank you all for the support. It means so much! 💕