There is no common law marriage in Georgia. It was abolished as of January 1, 1997 - 16 years ago (as of 1/1/13). You state that you have been living with your boyfriend for 15 years. If your 15-year statement is accurate, then, by definition, your relationship would be outside of the 1/1/97 cut-off. A family law/domestic relations lawyer will be better-suited to discuss your rights with you in more detail, but I did want you to know that regarding the abolishment of common law marriage in Georgia.
Regarding the landlord-tenant issue, if you are not his common law wife, then you are, in fact, only a tenant, subject to being dispossessed of the premises. If you have no written lease with your boyfriend (with him, as landlord and you, as tenant), and If he intends to treat you as a tenant, then you are due to receive 60 days' notice to vacate the premises.
Know that I am sorry to share this, but maybe a family law attorney out there may see something that I do not see. Again, I recommend that you seek counsel from a family law attorney.