I think I am going through a very depressing time and I dont know why?

I am currently 17 and I am about to graduate from highschool. I believe I have a lot of problems in how I unconsciously react to things and the personality that is gradually taking form because of these reactions. I realize the problem I am about to describe is actually quite common for a lot of teenagers these days, but I do not know what to do at the moment because I am very well aware of myself and am willing to change.

First is, I find it hard just to have conversations with people. I can say I am a boring conservationist and I never blame it on the person I am talking to if the conversation ever turns stale. I am naturally quiet and will only act loud or obnoxious around the people I am close to. I am well aware of myself, always self correcting, eager to please, and always have believed I could do more to become a better person. I am very harsh on myself, one could say I am too soft, and always believe most problems between a relationship are cause by me.

Second is, I always find myself enjoying the company of new people, give very good first impressions, but do not exactly follow up. This is because whenever I meet someone new I feel a new surge of energy within me, but the energy usually doesn't last. With this being said, I find myself having problems with keeping long relationships or keeping them healthy. I don't have much energy when it comes to talking to people in medium to long sessions, and I don't really know how to make conversations last without making them turn boring or deep. With these two combine, I am always subjected to

The two problems addressed above do not exactly seem bad, or too weird, but with the two of them combined, I find myself having a very unhealthy social life. I have a good girlfriend who I am currently dating, and this social problem constantly makes me depress or easily irritated. I am very insecure, and my personality of eager to please and self correcting do not exactly help.

I realize this is not much of a question, but is there anyone that know what I am going through?