I see my birthday as my special day to do whatever I want, however I want. It's MY DAY. If that means calling up friends...I'll call up friends. If that means going skiing by myself...I'll go skiing. If that means buying a cheesecake and a 6-pack of beer for breakfast...guess what? I don't do anything I don't want to. But, I'm more than twice as old as you are and have seen many "traditional" birthdays pass. Most of them depressing disasters!
When I was around 20, I thought that people who were my friends would show me they were my friends by actually remembering the day, but I found out very quickly that I'm the only person I know who remembers birthdays and sends/gives cards and buys presents. That's depressing!
As for getting older, youth is overrated. Honestly, the only thing you have is health (I assume) and lots of energy. You lack experience, understanding, insight and a wisdom that only comes with years.
I'm not saying that to make you feel bad or say you are immature or don't understand anything! I'm saying what you understand now is only the surface. With the passing of years you will understand it all on a much deeper level. There is a LOT to look forward to about getting older!
Don't see it as the kilometer marker of your years to the grave...see it as a marker of your wisdom, experience and development as a unique individual.
I guess, that to not celebrate your birthday with friends or family is something out of the ordinary. If you really want to do it in a different way, you'll definitely meet the problems with an explanation to your relatives, because the first thing, which will come to their heads, is your disconnection from them.