Hello I'm Currently Pregnant And I'm Constantly In And Out

Hello I'm currently pregnant and I'm constantly in and out of hospital my chest is really bad and also I constantly got a high pulse varying between (135-160) a dr kept me in hospital for a heart scan as he thought I may have an enlarged heart however this was not the case and my heart is healthy so I'm very uncomfortable I have pulpataions and keep sweating and the Drs have no clue to what is wrong than to say it's my body reacting to pregnancy. Do you have any idea what could be wrong with me ?