Elective Amputation

I have some injuries that I sustained in a road traffic collision over four years ago. The injuries meant I required surgeries to pin and later unpin my ankle, and for skin graft procedures to my shin (it is, in fact, my leg that appears on the present Wikipedia entry for skin grafting - viewer caution, slightly gory). 

I spent eight months on crutches, and have not been able to walk comfortably since. The graft disrupts the lymphatic system so whenever the leg is not at hip height or higher, it slowly fills with fluid. Combined with joint pain in the ankle, I'm left with injuries which mean I can neither sit for long periods (without elevation) nor stand for long.

On many days the swelling is such and the pain within the joint so much that I can't focus well, and spend much of the day with intrusive thoughts, often imagining new and more gruesome injuries being sustained. Sometimes I fantasize about having the limb amputated below the knee. 

Since these fantasies are often sparked by pain, I got to wondering. What if...

Would some of my problems be alleviated if I were to ask, beg if necessary, my GP to refer me to a specialist who could remove an otherwise "healthy" limb? Would a specialist even consider this? Is quality of life a trump card over remaining physically intact? 

I can walk bipedally, and unaided for short distances too (I use a crutch to go more than around 100 yards since then the pain gets too intense and I need it to push on, and to balance, especially when the ankle gives out a little). However, despite this level of mobility which is apparently considered acceptable by some doctors, I can't imagine having to live for potentially 40-60 years more with the kind of pain I have now. 

I know I should count my blessings to be alive and have all four limbs reasonably complete and attached, but I can't help but feel it's simply not enough to live. I need to enjoy living.