Hi Annie,
I have had a similar situation a few years back. I had a brain tumor removed and my short term memory was very, very bad afterwards. I used a small kitchen timer when I cooked anything. This was to remind me not to go off from the kitchen for too long with something cooking. It really helped me. I became very good friends with the microwave and frozen dinners. Still, today, I have a system of checks and re-checks I go through when I am cooking. (I even go through the house at night before I go to bed and check the stove, all doors, TV, etc. to make sure all are off and locked!) Best wishes, and please try a timer that has a loud ring or buzz, Dodi