"Were" is incorrect. The correct past tense for first person singular is "was." You can use "were" in the subjunctive case, which is a situation where you discuss unreal situations. They will usually start with "if." "If I were young again, then I would choose a different path."

In some parts of the UK people say "when i were young" if speaking in a casual/colloquial register. Good to know, but not copy!