I totally understand (on many levels)! I also have 2 surviving triplets, they were born at 24 weeks. My 2 girls are now 3 years old and have always been HORRIBLE eaters and drinkers!!!! I have learned that micro-managing their eating is not helpful; and that they will eventually eat when they're hungry (even though it's not when I expect them to be hungry). It will seem like they've eaten nothing for 4 meals straight, and then they'll surprise the heck out of me. My one daughter is on this kick of wanting only cookies, popsicles, candy canes, and "treats." Every meal I offer a healthy assortment of foods, in addition to 1 treat. Sometimes they eat the treat first, sometimes they eat the apple first. But at least it limits the fighting and power-struggle for wanting a treat. It wasn't until this past October that they started drinking any real amounts of liquid. And when we were giving them the pediasure, it seemed that they drank so little but go so full that they wouldn't eat or drink anything else (so we discontinued that).
At 3 years of age, they both weigh 25-27 pounds. (We go to the doc next week for their well-baby.) Although I've been concerned about eating and weight for 3 years, both pediatricians we have used have been okay with their weight gain. (Although they are very light for their age, they are following their own growth curves and progressing.) I have never been referred to a nutritionist or specialist for this reason.
My only sanity is the philosophy that the only power that I have is to offer good foods to my children. It's their choice whether or not to actually eat the foods. I've heard this from one nutritionist that I heard speak, and have used it in my most frustrating of moments... and then walk away so as not to watch. If I'm more relaxed, so are they. (I also try to remember this when they're smearing their yogurt or pudding all over the place! I try to remember that it's good for them to play with and explore their food, even if a lot is not yet making it into their mouths. The good news - they will now eat an entire container of pudding!)
At and earlier age, I learned that sitting in front of the tv offered them enough entertainment to keep them seated during the mealtime - and they would pick at the food. I hate that it means having the tv on, but my priority has been getting calories into them right now (not tv watching). As they've gotten older, I realize that this sometimes backfires because they're too involved in the show and forget about the food in front of them - but it worked great when younger.
I wish I had more "advice." I would suggest talking with your doc about their actual growth curves instead of their weight. Also, if you're feeling that bad after doctor visits, I wonder if you would be interested in trying to find another pediatrician who works with you instead of blaming you? We switched pediatricians at 1 year of age, after our 1st ped confused the girls and was telling me to give one of them medication that was intended for the other. I felt horrible because she had followed us for so long, but have been very happy with the choice that we made!
Last thought: Remember that you are a good Mommy. You're obviously seeking a lot of special services for your children (nutritionists, OT, etc). It is NOT your fault that they won't put the food in their mouths! All you can do is offer, encourage and model.
Best wishes to you!