ive been in a relationship for 4 yrs and have a small crush on a dude in one of my classes. actually its not really a "crush"...just an attraction or lust. but knowing im sexually attracted to him i would never search for his number or try to go out of my way to talk to him. i think fantasies are normal for people in long term relationships to have. we're human and we're almost genetically engineered to want multiple partners..or have options.
but acting upon them is a different story. i think you really need to reevaluate your relationship. i would feel weird knowing my boyfriend was desperately trying to text a girl he found sexually attractive or had a crush on..im sure he would feel the same if it were vice versa. there's times where i feel my relationship is too comfortable or getting stale (4 yrs is longer than most ppl think lol..feels like 20) but i always communicate with my boyfriend about it as he does me. i think you said you dont want to break up with your current boyfriend , then communicate with him...tell him in a nice way you want to spice things up or want to bring more of a spark into the relationship. chances are he probably feels the same.
and stop trying to pursue other men you find attractive. that is wrong. like i said fantasies are one thing, but it seems to me you have the intent to cheat. good luck.