Is it possible that some people are just going to be less happy then others?

That's not true. We can't say that some people will be less happy than others because we are all different and we are always changing. For you it seems that you are not changing. You might be less happy actually but that doesn't necessarily mean it will always be that way. A lot of people I would consider to be happy are not that happy. I'm like you in a way. I struggle with depression at this point in my life. I don't consider myself to be happy or unhappy just as you said. Believe me when I tell you that happiness is more of an ideal than a reality. But there are some people who are truly happy. I wish you were more happy. You could try to make jokes with people and laugh. That's what makes me happy. Or watching a movie and laughing at the funny parts. If you can't laugh then try to get yourself happier. Drink a lot of coffee or a red bull or two. That might give you an extra spark. I think that true happiness has to do with the fulfillment of dreams. So good luck.