Hi Jenny,
I assume a the low grade tachycardia means you are about 100-110 beats per minute? Tachycardia usually does not cause elevated pulmonary artery pressures although I wonder why your heart rate is elveated (thyroid, anxiety, pulmonary disease, inappropriate sinus tachycardia, etc) 35 mmHg is considered mild pulmonary hypertension, but is still very low. I don't think it is the primary cause of your shortness of breath. It may be worhty looking into other causes--pulmonary? rheumatic?
I hope this helps.
Good luck.
Just my two cents worth.