1991 Mazda MX5 Looses power

My car looses power on the highway, traveling at 55 -65 then it loose speed. Giving it more gas doesn't help. I've had to pull over and just wait. It has been getting worse over the past couple of months.

The car isn't driven far. Maybe 100 miles a week. I've had this happen on morning when it's cold and damp outside. I've had it happen when it's warm and sunny. The car has been wrecked in the left rear and had lights and quarter panel replaced.

I only purchased it last October. I have all the service records. I just wondered what you thought.