Proving Jewish ancestry…stressful! Family from Ukraine…help?

Proving Jewish ancestry, very stressful! What to do??

So I’m trying to get married and I’m trying to verify my Jewish ancestry though Chabad’s program, Jewish status or whatever. My mom was born in Kyiv, Ukraine, moved to the US when she was 15, and has a ketubah from her marriage with my father.

Her Soviet birth certificate says both her parents were Jewish, but the Chabad Rabbi says we need more proof that my grandmother was actually Jewish. He says that apparently in the Soviet Union it wasn’t uncommon to list both parents as Jewish even if only one indeed was. Is this true?

I’m at a loss for what else to do. My grandmother’s documents were all destroyed by the Nazis, and and we don’t have any documents regarding my great grandmother. I am extremely confident my grandmother was Jewish, she has memories of her parents praying in private, of them counting out the days between the Chagim, etc. Plus why would she have married my grandfather if she wasn’t Jewish? She said she recognized him as Jewish right away, and then they were married a month later. She says her mother’s maiden name was Kaplan, though we don’t have any proof of this. Her maiden name was Malyar which is more of a Ukrainian last name, and there is some speculation that maybe her father wasn’t Jewish.

I’m having a huge identity crisis here! I know I’m Jewish, of course I’m Jewish, but am I going to have to convert so that I and my kids have a clear matrilineal line? Help!