5'8 Female 142.00

Recently I have lost a good amount of weight. Went from 209.00 to 142.00 but the problem is... I don't feel any different. Granted, I fit into a small clothes, I mean I have never been a size four dress EVER. It's nice but my problem is I don't know if I should stop there or keep going? Is 142 too small for my height?? I am so terrified that if I stop dieting and killing myself at the gym that I will gain all that weight back, plus some. Any suggestions?