I feel you. I had a similar episode when I was 28 weeks pregnant. Felt like I couldn’t breathe when I was travelling in a car. It felt so claustrophobic. I had to force myself to take deep breaths, adjust my seat position, wind down the windows and think of something else. I think it had to do with my big tummy pressing against my chest when I was in the car. Since your medical checks are ok, no need to be scared! Try to think of the triggers that may cause these panic attacks and avoid them if possible. Relax and think positive. Think about your baby, think about the joy and laughter in your life...