Relationship Advice

Hey girls, I need advice. So I'm 20 and in college, I've been dating my wonderful boyfriend for 4 years! I adore him so so so much. I noticed I got a lil crush on someone at college. It's a small college (abt 2,000 ish students) so it's hard not to run into him/talk to him bc he's been in a few classes of mine. Any tips on how to ignore this feeling? I feel so guilty after having the slightest thought abt him. I don't feel like it's fair to my bf to prolong this feeling for some guy at school (esp bc we have been planning our future w each other this past year, so it's a bit serious). Have you ever gotten a crush when you were in a partnership or married and had to force yourself to ignore it? How did you do it?