I believe I have the same problem that you have. I have been "underweight" and lacking in energy my entire life. I had developed intestinal ulcers which felt like appendicitis (I think) for 1 1/2 years. I didn't make the connection with gluten until recently, as I began to develop joint problems and then I read about Celiac and realized that I had many, many of the symptoms.
I have been gluten-free for almost 3 months, but have been approximately 80% raw for over a year, so I had significantly reduced my gluten intake gradually beforehand. My ulcers are almost gone. My joint problems are completely gone. I don't bruise as easily as I used to. Since I purchased my scale a year ago, I hadn't been over 96 pounds in the morning before eating. Now I am approximately 97.5 pounds in the morning.
Keep with the gluten-free. It gets a lot easier when you find good substitutions. Be wary of gluten-free products that contain too much starch, as I believe the excessive starch may hinder intestinal healing. It takes a while for your intestines to start healing, so don't be discouraged if you don't see results right away. You can help your intestines along in the healing process by occassional fasting and/or eating only one cooked meal a day. I also have been eating slippery elm, which is supposed to aide in the healing process. I get mine from shopnatural.com, but you may be able to find it less expensive elsewhere. Mix 1 tablespoon elm powder with 1/2 - 3/4 cup warm water and stir well, add cinnamon and honey (or other sweetener) to taste.