|Look, m8, I'll tell you one thing... or lets make it few things.
In my opinion, you don't have the right to be depressed. Maybe, however, a bit frustrated and annoyed at certain things in your life.
Every time you feel depressed, open up your tv, and watch the news. How many people are stuck between wars with no shelter or no food or parents? how many people there are dying from starvation or aids or just poverty and living on the streets under the garbage without the care of the society? look at the palestinian people, children living on the street, fighting tanks ignorantly with stones, mothers cry all day and night... You don't have the right to be depressed. Those have the right to, because they don't have anything (almost).
And why would you even care about friends at your age? friends are "nice" to have, but not neccessary, girls? sure if you are looking for a one night stand girl, just go to a night club and pick one, or strip club or whatever, or are you looking for marriage? I'm sure it's not a problem for a man in your standings, have job and money seems financialy stable and smart. When you find this right woman, you, sir, begins your life. What do you need more? you have a job, a wife, kids, money, a house ... and if you still get mad about people not liking you, well you can say in your mind the same thing I say to myself "they can f*ck right off. I don't give a caca, they don't deserv me." and suddenly I feel very happy and satisfied with myself. maybe you should try this strategy.
whenever you feel depressed again, try seeing things from my point of view, because I been there at a much younger age, now i'm 23, and I've had friends like that and told them the same thing, I don't recall them complain about depression to me again.
however if this insists, it might be something physical/chemical in your brain and might want to see a doctor. Goodluck.