>>20284
Narrated Abu Huraira:
The Prophet (ﷺ) said, "Allah has accepted my invocation to forgive what whispers in the hearts of my followers, unless they put it to action or utter it." (Sahih al-Bukhari 2528)
You should try to control your fantasies, but no it isn't "haram" per se.
Akhi, get a wife.