is there any Jewish source about birthdays and how they should be celebrated? or why they should be celebrated?

There is mention in the Gemmorah of some who celebrated milestone birthdays such as 60th or 70th otherwise there are no other sources or basis for celebrating bithdays

I think i remember hearing/reading that a birthday is a time for introspection. Not sure of source of it though but it can't harm

is it your birthday?

There is someone who definitely says (I forget at the moment who - I may remember later...) that on one's birthday, one is granted more linkage to Hashem, so that if you make your learning, davening, and general activities that day extra special, you may reap the benefits soon after

In Chassidic circles, we view a birthday as a personal rosh hashana in which should be treated as such. We really should not see it as a time of senseless celebration, but as a meaningful experience like rosh hashana. So it is best to do so in this way. Many charedim also do so in this manner as well as in other circles of Orthodoxy. But it should be a meaningful time to really find a closeness to Hashem that we may not have had in the year before and do some soul-searching and make the next year better. Oh and by the way, we should make a special prayer to Hashem thanking Him for giving us life. To celebrate it in any other way is like the person saying that they deserved to be alive and they are also taking credit for living so long. Why we live to that certain year is based on the sustenance of Hashem.