He still loves you. Even when you broke his heart by rejecting him many times. I know you didn't expect him to fall this hard for you. I know you felt like you led him on simply because you were confused at a certain time; you felt comfortable that someone cares this much for you, you almost thought you liked him back. However, you realised you didn't feel the same way for reasons you know (or don't) but there's a gut feeling that tells you, you two are not meant to be. And so, with a heavy heart, you rejected him again and again. Softly at first, then harder next. Because he needs to know the truth: you're just not that compatible.
Then you meet someone else. You feel it, don't you? This time it's real. But he's still pining for you. I know you feel the guilt slowly suffocating you when you watch his crestfallen face when he catches you looking at your partner adoringly. I know you feel bad but he'll find someone else. You can't force yourself to like him back, no matter how sweet he is to you. It's a messy, confusing and painful experience but it's inevitable. You just need to give some space for both of you to untangle the knots. Give him time to heal. Eventually both of you will find your own happiness, and you know it isn't from each other. Someday the love he gave you will come back to him in waves and he'll be thankful you rejected him. But for now, it isn't anyone's fault.
-m.b
Unrequited love is a painful thing to go through, on both sides. It takes a lot of time and will to get through it, but you'll get by