Can I take my ex boyfriends last name and do we share anything?

The short answer is no. Living with a boyfriend does not entitle you to half of what he has. It is possible that you discussed this issue with someone who misunderstood common law marriage, which requires more than living together and one person trying to change their name. That being said, you may have rights to any property you acquired together, and if that applies to you, it may be worth your while to discuss the matter further with any attorney.