Help me!!! Please I want to become fatter?

Ok, so I'm 16 (girl), exactly 5 foot, and weigh about 90 pounds. The average weight for a 16 year old is about 120 pounds. Im a vegetarian so I don't eat meat or fish. ALso, i dont eat eggs. How can I raise my weight? I'm very healthy, I eat A LOT , but I have a really high metabolism. I don't do that much excerise, but about twice a week, I'll proababyl go to the pool and swim 2 or 3 hours. And I don't try to not eat, either. Actually, lately I've been trying to eat more junkfood, but that hasnt really helped