Why am I like this?

I love this guy we have been talking for months. We both really love each other. However, I got issues because when he gets busy or has to do something, I can wait an hour or two or three but any time after then, I start getting really upset or mad. I know people have things to do, people to see, places to be etc. but idk I sometimes get upset because I always want his attention.

I overthink, thinking he doesn't love me anymore but also generally I get upset because I want to spend my time with him a lot. I end up getting really sad and sometimes even mad.

I don't need people to tell me that the way I think is wrong and not right. I already know. I am trying to fix myself and make myself stop doing this. I have started improving recently.

I always want them by my side spending time with me even though I know that it is not possible to do this all the time.
We love each other very much but I keep messing up for being like this and he is getting tired of it, which I understand. He sometimes thinks he is not enough for me. He almost cut me off because of this problem that I have.
I am trying to improve and be a better person. I don't want anyone to come at me for how I am because as I said, I'm improving and I already know I am in the wrong for this.

I just want to know why have I found myself attached to this person and why I get upset when they haven't talked to me after some time. I know it sounds dumb. Any advice for this problem?