General distress:
* Upset
* Anxious
* Worried
* Troubled
* Agitated
* Uncomfortable
* Uneasy
* In distress
* In pain
More specific distress:
* For a person: Dejected, despondent, heartbroken, miserable, unhappy, despairing
* For a situation: Difficult, dire, desperate, grim, precarious, critical, severe, painful
* For an object: Damaged, worn, faded, torn, broken, shabby
Informal synonyms:
* Stressed out
* Freaked out
* Bummed out
* Down in the dumps
The best synonym will depend on the specific situation and the intended meaning.