Had mitral valve repair done. Still have mild leak shown on echo will this cause shortness of breath been 2 months since surgery.

Possible. But keep with cardiac rehab to regain cv conditioning. Possibly still some anemia- iron and vitamins. Fluid retention should be resolving. No smoking, weight control, regular followup peripheral vasodilation may further reduce any regurgitation. Your cardiologist will review and recommend.
It depends. It depends not only upon the degree of the mitral valve leak but also upon ones blood pressure. If the blood pressure is kept in the low normal range, one should not experience significant shortness of breath from the mild mitral leak.