You're not a failure, I also found establishing breastfeeding horribly difficult, I think many mums do.

Have you been to see your GP about the mastitis? It's really important to get on top of it asap and you will probably needs some AB's. Cabbage leaves (just tucked into your bra) are great for relieving the inflamation, and I also found heat packs on the blocked area before feeding then massage prior to and during the feed really helped to clear it. But it took me a good week to get rid of the lump altogether so perserverence is really important

I also had terribly cracked nipples for the first few weeks. I saw a LC a couple of times who told me our attachment was perfect, but I was still getting the cracks. To help stop the cracks from getting infected I would bathe my nipples in a salt water solution. A medicine glass works really well for this because you can put the solution in and then put the cup over your nipple and give them a really good clean iykwim.

In the end I found nipples shields to be a lifesaver. I wouldn't have been able to continue breastfeeding without them. I used them full-time up until about 8 weeks when I gradually started to wean DS from them. I started off just doing one feed a day on each side without it and then built up to two, then every second feed, until he was 12 weeks and we were finally able to say goodbye to them.

I also gave my DS expressed milk in a bottle on occassions. For us it didn't cause any problems with breast refusal, but I do know for some mums it does. Like the others have said bfing really does help to clear a blockage so try and do that if you can, but if every now and then you need a break one bottle every day or so shouldn't do too much harm.

Try not to get too down on yourself. Mastering breastfeeding is no easy feet. Just keep trying and do all you can to get rid of the mastitis and heal your nipples. Good luck x