You have all the classic symptoms of anxiety disorder. The shortness of breath, fogginess, heart racing, getting flush...all bodily symptoms of anxiety and panic
It's a good idea to rule out anything else medically but chances are, as your doctor already said, you are probably just fine. Many of us have gone through the same things including me. I used to go to countless doctor's visits thinking something MUST be wrong. In fact, they could never find anything. Mind you, this was in the days when anxiety disorder wasn't even really known or talked about...I'm talking about 20+ years ago when anxiety/panic disorder was a "new" phenomenon.
Some people have bouts of anxiety/panic that come and go. If this is you, then it sounds like you need to find a way to ride it out...maybe relaxation, meditation, positive affirmations, family/friends support. But if your symptoms persist and it's not going away, then it might be best for you to go back on a low dose of medication. I've been on medication for more than 20 years. A few times, I would take myself off feeling like it was weakness if I took something, but inevitably, the anxiety/panic would come back, along with severe depression. So now, I've accepted that taking medication is a lifelong commitment.
Hope this helps in some way...hang in!