のは私だけ

I'm the only one who...

→ の
phrase Rare #32,963
I'm the only one who... のは turns the preceding clause into the topic, and 私だけ means “only me.” With じゃない, the phrase means “I'm not the only one who...”
JA: この映画を何度も見たのは私だけかな?
EN: Am I the only one who has watched this movie many times?

トム好きなのは私だけじゃない

I'm not the only one who likes Tom.

たまにトム女の子に見えるときがあるのは私だけかな

Am I the only one who sometimes thinks Tom looks like a girl?

笑ったのは私だけだった

I was the only one who laughed.

トム太りすぎだと思っているのは私だけじゃない

I'm not the only one who thinks Tom is too fat.

仕事してるのは私だけ

I'm the only one working.