Is it possible to report a fake account without knowing its real identity?

For the second time, I believe I am being abused by the same person.

Someone is creating fake accounts and knows so much about me (no idea where from!) without me knowing who he really is.

He knows my family, where I work, etc. But he always avoids meeting me in person.

The first time I almost fell in love, but now it annoys me so much not knowing who he is and why he's playing with my psyche.

Can someone like this be reported? If so, what?

Thank you in advance for your advice!