What do I do?

I'm a male 19, I used to Starve Starve myself a few years ago (at 16) because I thought I was fat, I got help with camhs and I started eating more again, much recently tho I just really can't eat, my body doesn't want me too even swallow I'm loosing weight fast and I weigh 7 stone exactly, the lowest I've been it's 7 stone 3 and that was over 3 years ago, idk how to eat without panicking, I want to eat but it just seems impossible like I'm going to be sick, what do I do? I Want to gain weight and I want to be healthy I just don't know how it's possible