I can understand your situation. It is suggestive of a condition called premature ejaculation. The threshold for ejaculation is low and minimal arousal can often lead to spontaneous discharge. Anxiety and stress happens to be some risk factors for premature ejaculation.
Next Steps
Kindly consult with a sexologist for further management and detailed instructions. With suitable medications and instructions it can be completely cured. For more information regarding this problem you can ask a detailed query here on practo.
Health Tips
Don't worry. It is treatable.