I think it's time we talked. It's been four months and you've been torturing yourself over him. I want to let you know a few things because I know you will refuse to reach out and talk to anyone. You have them convinced, and for a while yourself, that you're okay but we both know that for some reason you aren't able to get over everything.
I want you to know that it's okay that you are still pining over the boy that you almost dated, and it's okay that seeing him move on with a new girl hurts. You had been so happy in those few months with him and your mother used to tell you that you radiated whenever you talked about him. Also, it's okay that you thought you had gotten over him but at 3 in the morning you find yourself listening to sad music and thinking about everything that happened and could have happened. You two ignited quickly in a way that confused you and left you craving for more but then the flame went out and you were chocking on the smoke of your memories. It's okay that you're angry, he strung you along when he had another girl the whole time and you are allowed to be hurt by that.
However, you need to understand that it was not the other girl's fault and that she probably doesn't even know about what happened between the two of you. You also need to stop comparing yourself to her to see what's wrong with yourself. You are good enough and as soon as you realize that you will be able to move on. One day seeing him with her or seeing the posts he makes about how in love they are won't bother you. You will find another guy that will make you feel as happy and carefree as he did.
There will never be a right time for you two and you cannot go back in time to change things. He will always end up with her and you will always be hurt. This experience will teach you so much, you are so young and you have your whole life ahead of you. You need to let go of the pain you feel because it is not doing anything except making you cry your eyes out late at night hoping that something will change and you will be together, or at least that you will be happy.
Don't let this experience make you close off your emotions to everyone else. I know you try to protect yourself because it's easier to not feel then to experience the pain, but it isn't healthy. It damages your relationships and it slowly kills you inside. People will always hurt you but if you close yourself off you will never be able to find the people that light up your life and remind you why everyday you wake up and try to live a meaningful and happy life.
I want you to be happy and I want you to know that you do not need someone to make you happy. At the same time, I do want you to know that you are allowed to rely on someone else and you should open up your heart fully to everyone in your life instead of masking behind half-hearted relationships. I know one day you will find someone who completely changes your perspective on love and I can't wait till that day comes.