I think the ghosts started without you.

OP you need to clarify something very important - Do you live by yourself in your own apartment or room or do you share with anyone else. If you do live alone you need to get the locks changed (re-keyed) immediately. In that circumstance this could be considered a threat. Contact the police in that case. If you live with some others you need to tell the others what happened and that it is unacceptable. And if practical, get your room door lock changed to one with a real key that you can lock and is not unlocked without a real key - and do not share that key; wear it around your neck if necessary. It’s not that expensive to get locks re-keyed. I had our whole house re-keyed for a little over $100 when we moved in (prices vary with locale). And it’s not that difficult to replace a bedroom door lock with a whole new locking mechanism and doorknob. They sell them at the big box hardware stores for under $50. The only tools required are a flat and a Philips (cross-point) screwdriver. The instructions are in the package. Anyone should be able to follow the instructions.