You don't say how much you weigh, but are 10 or 15 lbs. really worth all this contemplation and effort?
Now that I'm old-ish, I'm horrified by how much time I spent when I was younger worrying about 5 or 10 or 15 lbs., that last little amount of weight before I reached perfection.
My friends and I sometimes comment about how, when we look back at photos of us when when we were younger, we are appalled at how much space the subject of our weight took up in our heads, when we all looked absolutely beautiful, and not overweight at all.
If it's only 10-15 lbs., I suggest that maybe your body is happiest and healthiest at this weight, and that maybe you are trying to reach an artificial ideal. Eat well and exercise, and enjoy your body as it is. 10 lbs. really doesn't make that much difference in your appearance, and older people don't look good when scrawny, anyway. Skinny only looks good on 20-somethings.