I'm really worried about my diet and appetite

Hi, I really need some advice from somebody that knows what they're talking about. I weight just under 7 stone if that's needed.

The past few weeks, I've been eating next to nothing, and only surviving on a slice of toast and banana every day, and I'm really worried that I'm in the early stages of an eating disorder. I've been getting frequent headaches, and I feel like I constantly have no energy, I even fall asleep at college sometimes.

I went to my local doctors, and she couldn't help me at all. I have emetophobia and I think that this is the biggest factor in me not eating anything because I'm usually feeling nauseous when I think about eating food. My mum says that it's all psychological and tries to force-feed me, but it never works and makes me feel worse.

I'm only 18, and I'm tired of feeling like this. I really want to get my life back on track for when I start university. So is there anything I can do to make me feel like a normal teenager again? I heard that there are pills that give you an appetite, but the doctor wouldn't give any to me.