Why do i feel so jealous of this guy Akshat and feel empty?

There is a guy named Akshat in my University where we are both pursuing MBA but we arent classmates. I am 23 and he is also within 22-24 age range. A few months ago I messaged this girl Ayushi on Instagram who is also in our University and she is also within 22-24 range. I just normally messaged her introducing about me but i didnt know she had a bf and never interacted with her in person due to being in different classrooms. She is Akshat's girlfriend. He confronted me in University cafeteria asking why i messaged his girl Ayushi. Even his friends who are my classmates asked me "Tuney Ayushi ko message kiya tha?" which means Did you message Ayushi? in Hindi language. I got scared and apologized saying I didnt know she had a bf and i already have crush on someone, so finally things got sorted.

But I am jealous of Akshat for dating Ayushi. Both are from North India living in Bangalore now and I am a Bengali guy. I had crush on this girl Akankshya in my University who is also within 21-23 age range but i found out she isnt into me at all and even avoided my phone call so i feel empty at times. Few days ago Ayushi had her birthday(either her 23rd or 24th birthday) and i saw someone posted a story of her wishing her happy birthday and she had such a nice pic with her bf Akshat. It makes me jealous and i feel i am missing out. Even Akankshya isnt into me and it sucks and leaves me with no options. It sucks that Akshat got such a cute gf like Ayushi and I am all alone.