Sounds very much like anxiety to me too. Traveling/driving used to be one of my big fears and I would Catastrophize about something as simple as driving past a particular spot on the highway where I felt anxious once, or worrying incessantly about planning ahead for trips,etc.
Your size and age really is not relevant, anxiety can strike people of any walk of life. Have you ever sought help for it through counseling by chance? It's a very treatable/livable affliction that many have overcome.