I was 80 pounds in 7th grade, I'm now 130 in 9th... and I can't gain another single pound! I know what you mean, I've been on diets, I've been working out, and I've kept up my basket ball, but I still can't do it. I've gotten bigger, a lot stronger, but I haven't gained more than 3 pounds for a year. I still get absolutely clobbered in tackle football.
I'm the same height and just a bit lighter, but I'm 14... and I can't stand knives. I think its got something to do with that I cut myself so badly (so many times); I was unsupervised with lots of sharp objects as a kid.