I Am Female, 37 Years. From Last Three Months I

I am female, 37 years. From last three months i am feeling severe short breath, fatigue walking only 300 m. I am diagnosed with 14 mm OS ASD and advised surgical closure. But my cadiologist says this shortness of breath and fatigue is not due to ASD. My Chest x ray and CT scan report are fine but mild PAH, with mild RA & RV dialation. Please help me to reach the clear diagnosis.