I'm in a relationship since 3 years but now I can't stop thinking about another boy. (He is in a relationship too.) What should I do?

An actual representation of my situation
An actual representation of my situation
I'm a 19 year old girl. So, my Boyfriend and I are together since 3 years. We love each other a lot. Our families also know how close we are. Everything is fine between us. Love and Lust, both are in perfect balance... like how it should be. But, recently I saw a boy and he is so fucking hot and attractive. I have seen him in person once and I have been stalking his Instagram account. He is kinda famous. He doesn't even know that I exist. But, I know almost know everything about his life because he posts everything on Instagram and also because I've some friends who know him or are friends with him. He also has a Girlfriend who he has been in a relationship since 5 or 6 months and it seems like they love each other a lot. Okay so now the problem is that I can't stop thinking about that boy. I tried to stop but I can't. I don't know how he is mentally. I mean I don't know how he behaves, talks or thinks in real life but he attracts me physically. I mean his body and looks attract me but, not the mind because I don't know him personally in real life. I love my boyfriend more than my life. I could die for him. It may sound cliche but I really would. I can neither leave him nor live without him. Then, why am I attracted to this guy? Why can't I stop thinking about this guy? Is it normal to be attracted to another person while you are already in a relationship? Am I in love with this guy or is this just attraction? Can we fall in love with someone just because of good looks or body and without knowing them in real life or never even talking to them? What should I do? How to stop thinking about this guy? Please don't say that to stop stalking him because I can't. I've tried that and I failed. I CAN'T STOP THINKING ABOUT HIM. Please say if this is normal? I'm so confused right now. PLEASE HELP.
I'm in a relationship since 3 years but now I can't stop thinking about another boy. (He is in a relationship too.) What should I do?
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