Filling full but haven't ate anything

I got sick on a Saturday night. Woke up Sunday afternoon with a little low grade temp. I was not able to eat but a couple bites of a banana. This continued Monday, Tuesday, Wednesday and into Thursday. I feel full but hungry at the same time. I will try to eat little things but I can't. I'm really scared because I really haven't ate since Saturday which was five days ago. Why do I feel full but haven't eaten anything

That’s the 1,000,000,000,000 dollar question isn’t it!? Doctors sure don’t know the answer. I have that feeling all the time, sometimes it is worse than others!  I hope you feel better soon! 

You made a mistake by eating even that banana, if you have an upset TUM TUM,

The first step is to stop eating for 24 hours, boiled water (cooled), sip it to keep up your hydration, and then start reintroducing food, gently gently, no meat, or anything spicy for a few days, so for example, some creamed rice, a poached egg.

Oh yes stay away from anything cooked in oils.

​Sounds like you managed to get a virus and or some suspect food, you will take a few days before you start to feel better.

​If not go and see a Dr.

Thank you I did ho see the Dr in the ER they couldn't tell me what was wrong with me

 Maybe you have picked up a bug.  Try sipping small amounts of milk to settle your stomach and bulid yourself up.   However, I would see a doctor if this continues.