Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
Everything is really painful right now. Why? You have something heavy on top of you, crushing (くる) you.
I ate too much and it’s painful.
I'm agonizing over the fact that I'm not able to confess my love to Tofugu.
To speak frankly, those are pretty agonizing circumstances.