Feeling of heart racing.. (med ?)

[Ari0825]

I need help. I have been to the ER for this and my OB-GYN, and all my tests came back normal.
I am 28 weeks pregnant. I get this feeling, no matter what I'm doing, sitting, lying, w/e. I feel like my heart is racing, and I have to catch my breath. They thought I had a blod clot. , but like I said all my tests came back okay. I still have this feeling, and it sucks, it kind of hurts .. and I don't knwo what to do.. they say everything is normal, but then why do I feel this way??