Does this sound heavy?

5'5'' ; 135 pounds, size 5

no your normal weight and normal size for your height!
weight and sizes go mostly by height so your good! just have a normal work out routine and keep a healthy diet and you will maybe lose or stay the same

unless if you're a kid, and then you don't have to work out. like, 18 and younger type of thing.
If you're going to school, hanging out with friends on the weekends, then that should be enough exercise for any teens.
Well, unless if they eat a lot of junk food and when they hang out with their friends they just sit around and play video games instead of walking somewhere or doing something at least somewhat active...
wow. sorry.
anyways, you're good.
Just... Keep up the good work I guess. ?

(:

It sounds pretty fit to me.

no you are fine. I'm heavier than you and I'm fine. Don't stress.