Hi,
You have identity in that you have your birth certificate, 15 years is a hell of a time to run but I guess you had your reasons. You do not deserve to be treated like s%&t though. Do you have a driving license or passport? if you want more identity you could try getting hold of these. I know these things cost money. I assume the army discharged you, therefore they technically fired you, I suspect though you have not been paying taxes since you could not leagally work which will cause problems with work, what were you doing during your time on the run? can you do this as a civvy? Not wishing to offend but you could always try McDonnalds/KFC/Burger King, these companys offer on the job training and a wage (all be it basic), it would however get you working and you would start to gain skills/experiance. If you have any other thoughts/questions. Post them here, It might seem quite but I'll be you there are lurkers in here that could help you more.
Take Care
Robin