First - Don't stress and don't feel guilty.
Second - ITs YOUR choice so if you REALLY don't want to breastfeed then don't, NOONE is forcing you, well I hope not anyway.
Thirdly - you can call your local parents helpline on choices to help you through this and maybe have someone come and visit you at home.

My little girl is 6mths now and has been bottle fed since week 2 as I had a lot of the same feelings as you and she was feeding for over 2 hours each time and still was hungry, so I came to the conclusion of what was best for my sanity and her well being.

We can't tell you what you should do, thats the choice for you, but I can let you know there is nothing wrong with formula feeding, as you can see in my signature my little Maya is thriving and incredibly happy!

All the best in your decision.