GMM, you're doing really well, you know - I know it doesn't necessarily feel like it when your eyes don't work you're so tired, but you really are.
It's entirely your decision whether you give your baby formula or not, of course it is - but before you do, look to the longer term - how did you feel about bf before you had your baby? Was it something you really wanted to do?
How about in the last couple of weeks? How have you felt about bf?
And in the next couple of weeks/months? Were you planning on weaning onto formula before solids, or continuing to exclusively breastfeed for a while longer?
I know how hard it is when you haven't had sleep and you've a baby latched on most of the day, but I don't want you to give formula unless it's something you're 100% happy doing and you're sure you won't regret doing it once you've had a bit more sleep.
But you are doing really well, you know. And this bit's really hard. But it's very worth it, I promise.
Have you tried lying down to feed? It's worth learning to, IME - I didn't manage it with DS1 till he was about 4mo, but I did it with DS2 from birth - I made sure I kept trying till we cracked it, because I knew how much easier it was to be lying down and drowsing in and out of sleep while the hungry little blighter fed and fed.
Keep posting - thinking of you.