It is perfectly fine to be vegan - it's your body you can do what you want with it but please make sure you know what you're doing and about nutrition and alternative sources of things. You should go see a nutritionist. Besides the obvious things like calcium and proteins etc there are also other less known but still important essential nutrients
It would be better to start off getting it right than getting sick and someone force feeding you something you don't agree with because I am sure they don't put vegan feeds down tubes.