What is corrosion of the cervix? and who gave it to me?

Erosion: You probably mean erosion--which is a superficial ulceration or loss of the lining of the cervix. This can be caused by many things from infection, inflammation, friction, tampons, pessary, etc. It is not necessarily "someone" who caused it, although rarely sexual intercourse may result in post-coital bleeding due to trauma of the cervix.