I agree with Celle. You need to be seen by a good revision surgeon. Who was the surgeon you saw in Boston? I'd like to look him up and see what experience he has with problem knees.
Actually, it may be worthwhile for you to be tested for metal allergies. Unfortunately the cost is rather high ($573) and it's usually not covered by insurance. But if you don't have any obvious reasons for the pain, it is good to rule out a sensitivity to the metal implant.
If you'd like me to help you find a couple of revision surgeons to talk with, I'd be happy to. Just tell me when you're ready to make an appointment and tag me so I see it quickly. If you don't mind traveling to Boston, that's an excellent place to find good surgeons.
And....that doctor who told you revisions are way more painful than a primary TKR....that tells me he's not done very many of them because our experience here on the forum is that the recovery is no worse than a primary knee replacement and many times actually easier. Please don't let that worry you.