That happened to me on my 16th birthday... except nobody asked me for money lol turns out though that everyone was ignoring me on purpose for a surprise party later on. I don't wanna get your hopes up, but MAYBE that's why?
Do you have a facebook and if so is your birthday posted? That helps a lot lol
Have a great birthday and don't let it get you down cause there are clearly a lot of people here on FML that care to wish you :)