I just read that a doctor in New York had 13 lawsuits pending against him. If I bring a case against him too, does this mean I'd automatically win?
No. Every case is different. However, when a doctor has become a frequest guest of the Court system, everyone involved in the process (the attorneys, the insurance companies, the Court) gets a particular idea about the type of doctor this is and what a jury is likely to do at trial.
This does not mean that we can use all or some of his other pending cases against him in your case, but there may be some similarity with one or more cases that might justify addressing it at trial.