Is it good to go for a diet even when i'm under weight??!

Is it good to go for a diet even when i'm under weight??

i'm 50 kg...n 173cm tall...i don't really diet but i exercise a lot... i always think i'm fat... so i skip my meals...i only take my lunch n dinner that's all... but will it kill if i keep goin on like this?

I'm terrible for skipping meals but it's unhealthy and I know better having been trained as a Nutritionist.
You are underweight and may have fallen into the horrible claws of eating dissorders. Why do you feel overweight or fat? Have you had comments? If so, tell the people polietely to keep their comments to themselves.
You do not have to diet - just eat properly. First off (and even I'm bad for this) do not skip breakfast - even a small bowl of cereal and glass of juice is fine. Keep on taking lunch and dinner as usual with normal portions - don't skimp on them. If you skip meals, your body goes into starvation mode and it is afraid there may be no food for a while so it stores what you have taken in as fat. So skipping meals is a no no.
If you like to exercise then, please, please get some high carb foods into you before you exercise. You need the carbs to give you the stamina for exercise.
After exercising, you MUST get some protein into you. You will have lost some during the exercise and your body needs protein - that's the most important thing. Do this every time you exercise. If it means, 6 small meals a day then that's excellent - that was the way man was made to eat anyway - not 3 huge meals.
Please see your doctor and tell him/her of your concerns and they can advise you properly according to any health problems they are aware of.
My main rule now is to eat before 6:00pm and not after, with the exception of an apple or maybe a small bowl of popcorn while watching a film. Just enough to get you through the night.
Good luck.