My father experienced the same exact thing as you. He's mildly claustrophobic, which didn't develop until his 60s. The first time on a regional jet he just had a to get out. The FA was extremely helpful and suggested he try sitting in the first row. Somehow not seeing the entire length of the cabin, or lack thereof, helped him and he made it through the flight. Unfortunately, he won't go near a regional jet anymore, which makes planning his travels a little tricky in this day and age. He has no problem with full size aircraft.
Maybe sitting near the front helps. Who knows.