Document everything, even if it means getting statements from your friends, co workers and landlord.
Go to your police to check out the 'Stalking Laws' in your state. Ask for their advice and if they deem it is time to file a restraining order. Give them the whole story and STRESS your fear of him, that he has resurfaced after 3 months.
If they yes, go to the court and get one. It will be a Temporary Restraining Order or Protection Order (TRO or TPO) for about 3 weeks or so, when another court date will be held, he will have been served and be expected to be there to say why a Permanent Restraining order (PRO) or Protection Order (PPO) should not be granted.
I also like Fathom's suggestion of talking with your Landlord.
J M H O
Please keep posting and let us know how you are doing as we do care very much.
Love and hugs,