quitting breastfeeding?

Baby is 8 weeks and I am thinking about quitting breastfeeding. I switched from BF to pumping a few weeks ago because baby was getting really frustrated BF plus I wanted to know how much milk she is getting (she wasn't gaining weight very fast). Pumping has been better but really time consuming and it's starting to take a toll on me. It's leaving me exhausted (and sore) and I feel like I am attached to my pump. I can't go anywhere for long before heading back home to pump. I am debating about switching to formula or supplementing but the guilt is getting to me. My body is producing enough milk to BF and I know it's the best option for baby. Is switching to formula just for more freedom and sanity enough of a reason? Or does that make me a bad mother to quit and switch to formula when my body is producing enough milk?