@clairindespair - you have NOT let him down! You are going through a very difficult time, but you have reached out for help - that is the best thing you could do. And yes, mum guilt is terrible - I felt like a total failure as a mum because I couldn't breast feed any of my boys - they simply didn't put on weight on my milk, and the middle one even ended up in hospital (we went in because he had a chest infection but they kept us in because, at 6 weeks old, he hadn't regained his birthweight, and they said he was failing to thrive, which terrified me).
I was involved in the NCT, and had a number of friends with babies of similar ages, and, without exception, they were all breastfeeding with no problems whatsoever, and their babies were thriving - and I felt like a total failure because mine only put on weight when I introduced formula.
I had to make my peace with not being able to breastfeed - and now I look at three healthy young men, and it is clear that, even though I was not a perfect mum, I was a good enough one. It's right to try to do your best for your kids, but we shouldn't beat ourselves up when we aren't perfect - because no-one can be perfect!
I'm glad the Infacol seems to be helping - if he is more comfortable, he will be more snuggly, and that will help a lot with the bonding.
Find the things about him that give you pleasure - I used to love the soft, velvety back of the neck - it is so lovely to stroke little babies' necks. And as they got older, the little fat thighs were a source of pleasure for me too. Lots of little pleasures add up to happiness.