What Causes Abnormal Behavior Of A Person After Using Cocaine?

Hi, My boyfriend and I have been going through hell for about 6 months. Started with him being a real jerk out of nowhere, then he started accusing me of cheating, and using drugs for months. It eventually progressed to a full blown delusional disorder where he thinkd me and everyone else, my sister, his mother, siblings, people on the street are signaling someone. These signals are normal gestures that he reads as something else. He also sees things change in the house that didn t. The jealousy end got so severe that every time he wakes he thinks I snuck out... even is I go downstairs to pee for 3 minutes, he asks if I just f@Q$#ked someone. it s all day, non stop. I eventually figured out this was brought on by cocaine use (I think) and he has been using for about a year, but more and more lately. Well, he has been clean now 13 days and staying at his moms house. We have been still trying to work things out. I have honestly forgiven him for all of this... most of the symptoms have stopped or lessened. Except he still insists I am unfaithful. He still accuses me of having another man, or men, and he thinks I am with someone sometimes...even if I am on the phone with him or texting him. He asks if someone is there with me. It seems like most of these issues are going away, except for with me... should I continue to try and support him and reassure him, or should I just go away? we have children together and up until the cocaine use were perfect for eachother. I miss the guy I fell in love with so much! Will he ever stop thinking I am sneaking around and unfaithful?