Formal:
* Je suis frustré(e). (This is the most literal and neutral translation.)
Informal:
* Je suis énervé(e). (This translates to "I am annoyed" or "I am angry", and implies a higher level of frustration.)
* Je suis exaspéré(e). (This translates to "I am exasperated" and implies a strong level of frustration.)
* Je suis à bout. (This translates to "I'm at the end of my rope" and suggests a feeling of being overwhelmed by frustration.)
* J'en ai marre! (This translates to "I'm fed up!" and expresses strong frustration or annoyance.)
* Je suis au bord du gouffre! (This translates to "I'm on the verge of breaking down!" and expresses a high level of frustration.)
To make the expressions more specific:
* You can add the reason for your frustration: "Je suis frustré(e) parce que..." (I am frustrated because...)
* You can use different verbs to express the feeling of frustration: "Je me sens frustré(e)", "Je suis déçu(e)" (I am disappointed).
Remember that the best way to say "I am frustrated" in French depends on the specific context and the level of formality you want to convey.