You should be so proud to still be breastfeeding, i beleive its one of the toughest things to do in the world....but also the most rewarding!! I stopped b/f my girl at 18mths (she 2 this month), and every day i miss it. It is such a special time to spend with your baby, and i found as she got older it got more special, she used to look up at me after she finished drinking and say "milk all gone", i will cherish these moments forever.
I must admit if everyone around me wasnt a bit freaked out by me b/f a near toddler, i probably would still be feeding.
I suffered from PND for most of the last 2 yrs and i found that breastfeeding was the only thing that seemed real, it was the only thing that i could do for my daughter that no one else could.
I encourage you to feed as long as its right for you, when i have more babies, i hope i can feed for as long if not longer than last time.
Good luck and enjoy every minute with you baby, they grow waaaayyy too quick!