Option 1

Schedule a private meeting with Alex to calmly explain your perspective, reiterate your need to focus on your own duties, and suggest finding a collaborative solution that benefits both of you.

Option 2

Report Alex's behavior and the impact on your productivity to your manager or HR department, requesting their intervention to resolve the conflict.

Option 3

Avoid Alex as much as possible, hoping the situation will resolve itself, and continue to struggle silently with the guilt and stress.