can I sue my healthcare company for fraud ?

You can sue anybody for anything, but I don't think too much of your case for two reasons.  First, while the effects could have been catastrophic and I don't blame you for being angry, you did not mention having suffered any damages from the mistake (incidentally, it isn't fraud unless you can prove that the error was deliberate, which is unlikely.  In some circumstances, however, you can assert a claim for negligent misrepresentation).  It appears that you didn't go to the hospital in reliance on Aetna's misrepresentation, but you are apparently healthy now, and don't mention anything about having lost any money.  If I drive recklessly and hit your car, I am liable to you for the damages to your car.  If I drive just as recklessly but you manage to swerve out of the way, however, you have suffered no damages and have no cifvil claim against me. Second, you asked Aetna to tell you what was in your contract.  While that's common given the complexities of health insurance policies, you could have read the policy yourself.  That may not be realstic in today's world, but it nevertheless could be a barrier to your lawsuit.