Be at the end of your tether
Definition 1 of 1
Pro Tip 1/3Emotional Intensity
The phrase is used to express a strong feeling of frustration or exhaustion. 
I've been trying to fix this error for hours; I'm at the end of my tether.
Pro Tip 2/3Figurative Meaning
The phrase isn't about actual ropes or tethers but feeling restricted or out of options. 
With all these debts piling up, I'm at the end of my tether.
Pro Tip 3/3Overwhelmed
Use it when someone can't cope with difficulties anymore. 
If the baby doesn't stop crying, I'll be at the end of my tether.