I admire your honesty and openess to your experience. With more Mums speaking up about breastfeeding, it means we create more support for one another. I am sorry you have felt this way. Breastfeeding is a very difficult journey and is not at all straight forward. There are so many factors, health and emotional benefits within breastfeeding that I am certain you are aware of. You have done AMAZING to get how far you have. Don't ever put yourself down for giving formula, as you made that decision at a time of desparation - not to 'follow fashion' .
We will never be able to compare ourselves to how others' feel as we cannot live their life, however we can try our hardest to be as positive as we can for ourselves and our babies, especially at their first stages of life.
Now pat yourself on the back! There is no need to envy other Mums who continued to breastfeed for years, as it doesn't suit every mums wishes to do so for so long.
You have a superpower and you have not failed. But I do understand your frustration!
If you ever want to ask any questions, or are unsure on anything #breastfeeding related, give me a shout - that's what us mums are here for! :)