Why do i feel jealous of Akshat as he is in relationship with Ayushi? What can I do to stop the jealousy?

As I have posted previously that I messaged this super cute girl Ayushi on Instagram in January who goes to the same classes as me but we are in different classrooms. She is in the 22-24 age range and I am 23. She never replied to me but her boyfriend Akshat who is also within 22-24 age range confronted me about it last month and i apologized saying i didnt know that she had a bf and i said i have crush on someone else. We live in Bangalore in India so these are Indian names. Both of them are from Northern part of India whereas I am from Siliguri in West bengal which is in North-Eastern part of India. So things got sorted and he doesnt bother me about it again but nowadays i feel jealous whenever I see Akshat with Ayushi. I feel jealous that he has such a cute girlfriend whereas I am still single. I am way taller than Akshat too who is just about 5'4 which is below average height for men and I am 5'9 or maybe 5'9.5 which is about 3-4 inches above average for an Indian man. Even though I have crush on this girl Akankshya in the same institute who is also in the 21-23 age range and she is a lot prettier than Ayushi, i often overthink that I probably have no chance with her as she is too pretty almost model like and i don't even know whether she is even single or not.