The doctor here will (I hope) come on board to answer your question from his/her informed medical standpoint, but as a longtime PVC sufferer myself, I suggest you take a look at this discussion forum consisting of people like us:
http://www.medhelp.org/posts/Heart-Rhythm/pvcs-at-wits-end/show/358193
I also strongly recommend you read about PVCs here at MedHelp (just use the search box) so that you will understand that although these strange heartbeats feel awful, they are not dangerous. You are not going to die, and if you faint, it will be from anxiety and not from any heart problem.
You are accurately describing panic attacks, and although you may not know it yet, you are suffering much more from that than from the little boogie beat your heart is doing. For you to regain pleasure in your life, you are going to have to deal effectively with the panic.
Lorazepam will probably help, along with the Toprol, but the chances are that seeing a doctor who specializes in anxiety and who may prescribe a more long-term psych med (such as one of the SSRIs--google them) will give you the best relief.