About a year ago I found a disturbing implication I might be Jewish. I believe I now have an authoritative explanation. In Croatian, a cross before a year indicates the year of death and is usually used together with a star which indicates the year of birth. The source is "Croatian Orthography" by Babić and Moguš, 2011, page 113. I still think using religious symbols in this way is incredibly stupid, but I am relieved.
Here is my own experience with someone who became affiliated with Judaism from your part of the world.
The man was a Slovenian with a father who was perhaps Jewish, but only in part. The man worked as a metal machinist when Slovenia was a Soviet satellite, and then later was in the military, but he had antisocial traits which caused him to be cast out in one way or another, until he finally 'embraced' Judaism and somehow convinced the authorities to let him emigrate as a Jew.
He married an Israeli woman, of Iraqi extraction, but of a racial minority that perhaps resembles Europeans more than Semites (maybe Yazidi?). She was undoubtedly Jewish. She married him because he was uncircumcised, and remains so, and I assume that the novelty excited her, because she remains with him until today, eventhough he is openly unfaithful to her.
Now, most importantly, you asked how can one truly knoe if you're Jewish... Well, here's my test... This Slovenian man's son is an antisemite, so something inherent in this mans nature, or perhaps the subconscious antisemitism crept through during this boys adolescence.
In his aging state, the Slovenian more and more disassociates with Jews and seeks to reconciliate with Christians. He loves Putin.
That said, this man's efforts to "connect" with his Jewish roots shouldn't be taken lightly. This man speaks fluent hebrew -
better than me, and both my parents speak Hebrew.
Now I don't know you personally, you could very well be Jewish, but before you do anything drastic, I just implore you to look deep within your soul and ask yourself this question: If you had a son - would your son be an antisemite.