Unfortunately, the fact that there was a delay in sending out the tests is not reason for you to collect on the hospital bill or, for that matter, and "pain and suffering." CVS did not cause the strep, they merely were unable (due to minor negligence) to give timely results of the test. Their limit is likely whatever you paid for the test.
Part of the issue will be whether they intentionally delayed sending out the test (i.e., it was intentional such that you would suffer) or whether they acted in a way that was significantly out of bounds of industry practice (gross negligence). The way you tell it, it sounds like a mistake, not gross negligence.
I think, if you press, they'll refund what you paid... just to get rid of you. But, if you took this to court, they'd make the argument that they (a) did not cause the abscesses, (b) make an honest mistake in delaying sending the tests out, and (c) you signed a form that stated their limits of liability.
Take note of (c). Did you ever sign anything? I've not used CVS for tests, so I don't know their practice. But I've been to labs and they do require you to sign something that says that they aren't responsible for problems like this.

