Heart papiltations ?

Hey guys , does anyone experience shortness of breathe and heart palpitations  ? I’ve been getting heart palpitations since my second trimester and around 30 weeks I started getting shortness of breathe as if I were having a panic attack or something. Like I found myself fighting for air . I went to the ER about it and they said everything was fine. My ob wants me to get a echocardiogram but I’ve been having trouble scheduling an appointment with the radiology department. Hopefully I get one soon . I’m a little nervous because I heard of some women getting blood clots in their lungs . I pray it really is nothing . Just wanted to know if any other first time moms experience this