Under the laws of all states in this country, unless there is a written agreement between co-tenants dated and signed by each of them concerning the occupation of the jointly owned property by both of them, both tenants have the right to have access and occupy the jointly owned property.You are legally allowed to move back into your home. As an owner, you have the right to change the locks and give the other owner the key to the new lock for access. One wrinkle I see is the renter situation and where you place him or her for sleeping.I would write your former boyfriend about your intent in moving in again to your home keeping a copy of the letter and then move in on the stated date in the letter.