If you live in an apartment complex, notify the manager immediately. Give the same information as above. In addition, if anyone comes to your complex to inquire about you, request that they get a description and under no circumstance give out any information about you. Have the manger request an ID from the person. Although all managers say that they can't and won't give out any information, many do without realizing it.
Stalkers can be very charming, persuasive, and intimidating.
Over and over stalkers have impersonated repairman, delivery drivers, and law enforcement officers to gain access to victim's apartments. Change your routine. Don't jog, bike or walk the same route or at the same time each day. Don't shop at the same stores. If possible, have someone join you on your outings.