People keep telling me to stop losing weight?

So I'm 5'8, and I started out at 158 at my heaviest weight. I ate complete crap and didn't restrict my diet at all. In May, I started to work out a bit (nothing huge, just excercise bike and toning) and restricted how much I was eating. I never stopped eating or anything, I'm not anorexic. Now I'm down to 139 lbs and feel a lot better, but everyone's on my case about not losing anymore weight. I want to be around 135, but even my grandma noticed the weight I lost and kept commenting that I shouldn't lose anymore and while we were eating dinner she kept saying that I wasn't eating enough. Is 5'8 and 139 really that bad? Because I feel like it's not.