I am having I problem, the situation:

A couple of weeks ago, I couldn´t sleep, and in that moment I started kind of hallucinating, I didn´t knew what was going on, I heard strange noises and I saw things that did not exist. I knew what was real and what was not, but anyway I was very scared. Nowadays at night time I sometimes see scary things, listen strange noises and sometimes I feel as if I had someone behind me, when nothing of that is really going on. Can somebody tell me why is this happening to me? And please can someone give me an advice about what should I do?