What kind of doctors are you going to? Pediatricians, ENTs (ear/nose/throat), pediatric dentists?
Here's what happened with us, if it helps. We had our son's frenulum clipped at three weeks, even though he had consistent weight gain. Like you, I was in a lot of pain everytime I nursed, and after working with a pediatrician who was also a lactation consultant, we decided it was worth clipping. She wouldn't do it in the office, because it wouldn't be covered by insurance (?), so she sent us to a pediatric ENT practice at the local children's hospital. I just called and made the appointment myself, no referral necessary. The ENT took a look at DS's tongue, confirmed the tongue tie, and clipped it right there - there was little to no discussion of weight gain or breastfeeding. The pediatrician did recommend this specific ENT because she knew that he and his partner were willing to do frenectomies in the office without anesthesia. There was also a pediatric dentist she recommended.
My impression is that pediatricians in general can be less sympathetic to the pain that tongue-tie can cause for the mother. On paper, it seemed like everything was going fine for us - DS's weight gain was very good, and his latch even looked fine from the outside - but it was killing me. It took a while after the frenectomy for nursing to get better, I think due to both the damage I had suffered in the meantime and the time it took for DS to get used to his "new" tongue. But it was worth it.
I'd suggest seeing an LC, if you haven't already, because she may be more sympathetic and be able to point you in the right direction towards getting it addressed. Or maybe cut out the middleman and try going straight to a pediatric ENT doctor. Especially with twins, since the pain you're suffering is no doubt affecting your nursing experience with the other babe as well.
