Hi percieved increase in breathing is normal in pregnancy that can also be aggravated by anxiety. But since u convey extreme difficulty i have ruyle out any dvt pulmonary embolism or associated cardio vascular issues including anaemia in pregnancy ruled outby clinical examination and lab tests i.these days of swine flu and viral other pnemonia has to be ruled out finally i have to do physical exam rule out thyrotoxicosis get lab test of ft3 ft4 tsh done adjust thyroid replacement. As you can see it can be simple perception or something more serious hence visit to the gynaec is important.