Did you appeal the unemployment decision? If so, you'll get a chance to prove that you were laid off, as opposed to quitting.
As for the recommendation, there isn't a lot that you can do. For starters, you don't actually know whether he is giving you a bad recommendation. Even if he is, recommendations by former employers have considerable legal protection. You would have to prove that he is saying things that he knows are false, as opposed to expressing opinions.
If the dentist has 15 or more employees you may be able to file a claim for pregnancy discrimination. If he knowingly makes a false statement to another employer, saying that you quit, when you did not quit, you may also have a defamation claim. You can also appeal the denial of unemployment benefits.
This is not intended to be legal advice, but is only for general information. Cantact an attorney in your area for legal advice.