How to tell how much overweight I am?

look down and see if you can still see your feet

There are some trick scales around that measure body fat versus lean muscle. They probably have one at your gym. Ask your fitness instructor.

If not try one out at your local pharmacy, they cost around £60 upward.

Loose the weight you want to loose in order to feel better and still work out the way you want. Just monitor your measurements inc weight.

If you have the money, get a high-end body fat measurement. Or just have someone do a skin-fold measurement for you.

This article explores both and offers some resources:

http://www.webmd.com/diet/features/body-fat-measur...

You don't sound overweight to me, by the way

Have your body fat percentage checked. Muscle weight a heck of a lot more than fat.

What Saul Malone says is true.