Why am i having dreams of having sex with my ex-girlfriend when we broke up 3 months ago?

when me and my ex Girlfriend broke up 3 months ago and yet im having dreams of her & me knocking boots

Update: I thought if you broke up that you shouldnt have these kind of dreams because me and her are seeing different people and its already been 3 months seperated
Update 2: please leave comments of what you think whats happening to me because i want to know
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