I'm hungover, I have a bad headache, and I feel terrible. This is awful.
Koichi called out to Viet with his sickly sweet voice.
Stop bending your arms like that. It’s seriously weirding me out.
The 気持ち (feeling) is bad. So, you can imagine how you feel isn't good, it's a bad feeling. You're feeling terrible, in fact.
The readings come from the words 気持ち and 悪い. Hopefully you've seen both and can combine them together to know the reading automatically. No bad feelings with this word, right?