What are the laws regarding car titles, if the title was mailed to me instead of the leinholder by law is that car mine because I have possession of the title, and what if I stopped making payments can it still be repo'd even though I have said title?

You have a signed contract for a loan so the car can and will be legally repo'ed. I would call the loan company and tell them you were mailed the title by mistake.

Unless there is no lienholder listed OR you have a lien release, you still need to make the payments. The car can and will be repossessed if you fail to pay. Just having the title doesn't mean a hill of beans. I don't know what state you're in, but in Wisconsin, the vehicle purchaser always gets the title - doesn't mean they don't have to pay the loan on it.