You have absolutely the same symptoms as me. Having been breathless for several months I finally emailed our GP, had a phone call within days followed by a face-to-face. We tried antibiotics, which didn't work, and then, after an X-ray and an ECG, I was referred to hospital. I had scans, breathing tests followed by a face-to-face with a consultant, who requested 16 more blood tests. Yesterday I had a phone consultation and, after discussing with her colleagues and comparing the X-rays and scans with some done 4 years ago after a AAA, she has suggested trying steroids for 3 months.
The bottom line is, there are so many options for your symptoms, you need to get medics involved.