Normal in pregnancy or not ?? please help ?

Hi I'm 20 years old, and 30 weeks pregnant . For a while now my heart has been pounding in my chest several times a day even doubling up on a beat sometimes .. I have shortness of breath and I get intense pressure in my head like its so heavy . A couple of times I've gotten blurred vision .. once when I was at about three months and another time when I was about six months pregnant .. I'm tired all the time and sometimes I get chest pains .. what does this sound like ? Something I should worry about ? Is this normal in pregnancy ? I'm not sure .. this is my first pregnancy so I'm not sure what's normal or not. . I just fear I have a cardiac problem or something . Please help . :/