Costo is something I have sufered with for a number of years.
I have steroid injections into my chest for mine, but I have lots of other medical problems going on too and I personally find this is the best course of treatment for me.
Thing is I can well understand your anxiety but if the tests to date have proved negative for heart problems, then try to accept that. You say your dad died from having a heart attack, this is obviously going to make you so much aware of every pain and so on which is only normal in your situation. I would honestly take what the doctors and facts are given as being the truth.
I myself had a major heart atack, and 2 smaller ones and ended up having a triple bypass. I can tell you the pain from heart attacks/problems is nothing at all like rib pain. I am saying this to reassure you if I can.
You will get so much information about it on the Lupus forum on the board. Go to the top of the page, hit search and type the word in. You willl get varied posts there about it. This will give you lots and lots of facts and answer a lot of questions you may have. It is discussed very fully by myself and other memebrs who have it/suspect they have it. Having this to look into will then give you answers to a lot of your questions, and then in turn you can go armed with the data and speak to you doctor.
It is best done this way to find out from discussions between other members, as nobody on here can obviously diagnose you. Reading up on it in this way, and not looking on the internet will give you lots of 'first hand' information as I said.
I do help this helps you. Take care.