My guess is that men find you attractive and will continue to find you attractive just the way you are. You have a good appetite, you have a quick metabolism and I'm sure that your doctor gives you a clean bill of health at each check-up. So please use those facts to help fuel your self-esteem. Don't ever develop any kind of negative body image issues about it. You're healthy overall, and that's a good thing.
If you want to gain weight, gain weight. But do it for you and not for anyone else. If you want to stay the exact same weight, stay the exact same weight. Just focus now, and always, on your overall health. Exercise, eat healthy and diverse foods, get plenty of sleep and see your doctor regularly. Do those things right and you'll be just fine.
The men will be there, and they'll like you so long as you like yourself.
Ladies, any advice on being on the lean side of the spectrum?