I was very put of breath at 14-15 weeks the dr told me its a mix between the organs being moved upward by the uterus and the extra volume of blood that your body is pumping around.
Have you told your doctor? You need to go see the OBGYN and have a full history and exam done to rule out medical causes although rare they do occur. Keep a daily diary of time of day, activity you were doing when symptom occurred, how minor or severe the symptom was, what made it better..........until the time of your appoinment.