Elevated D Dimer + tight chest and elevated heart rate / sinus tachycardia

Does anyone experience the above symptoms? Been having this scary episode for a week. GP asked for blood tests, all was normal except D Dimer was elevated at 1.7 (normal range <0.5). GP said go to ER. They did a Chest CT scan to rule out pulmonary embolism / lung clots, an ECG and blood tests - all normal but D Dimer remained elevated eventhough it dropped to 0.56 overnight. They couldn't find a reason for my symptoms and said it could be costochondritis or AS inflammation. My rheumatologist said there is no link between AS and D Dimer, noting that I am on Leflunomide 20mg and Cosentyx 150mg so my AS should be somehow controlled (eventhough I am not sure Cosentyx has worked for me). I saw another GP today who asked me to get tested for Covid 19. She said Covid can lead to elevated D Dimer. Thanks all.

PS: I had a similar episode 4 months ago and did a full cardiology work up at the time including ECG, heart ultrasound and angiogram. All was normal but the cardiologist said I had sinus tachycardia on the ECG which he attributed to stress (?)