Miserable
Pitiable, Shameful, Deplorable, Wretched, Sad, Pitiful
You've seen how the word 情け means pity, so adding ない to that turns it into an adjective meaning pitiable and miserable.
なさけない
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You learned this reading already so you should be able to read it!
情けないですが、すぐに人を信じる性格なので、よくだまされるんです。
It's sad, but I have a very trusting nature, so I often get duped.
ツテでしゅうしょくするなんて、情けない。実力で勝負しろよ。
It's shameful to get a job using connections. You should compete using your merits alone.
日本の政治家には、本当に情けない奴が多い。
There really are a lot of deplorable Japanese politicians.