getting really irritated with my entire breastfeeding experience. my nipples are flat so she won't…

getting really irritated with my entire breastfeeding experience. my nipples are flat so she won't latch on (I've tried everything to bring them out) so I started pumping every 2 hours for every time she ate. I then developed mastitis in my left breast and now only make a few drops. my right breast won't make enough for a whole meal and my milk supply has been decreasing slowly. it's only been 3 weeks. I guess I'm going to just strictly formula feed soon. cause I've already upped my water intake and I've been eating oatmeal for the past week and nothing is helping. I feel like such a failure. even though I know I'm trying and my baby is eating well with formula. I just wasn't meant to breast feed😢