Will a delayed period be a sign of pregnancy?

Patient's question:

I am a female, 25 years old, and married.
My menstrual cycle is usually 29 days long. My period started on the 9th of October and then again on the 4th of November.
I traveled for work on the 7th of November when my period was still ongoing, and I had sexual intercourse only after returning on the 26th. I felt it was safe because it was the supposed safe period, and I didn’t use any protection. However, my usual period at the end of the month or the beginning of the next month hasn’t arrived yet.
I don’t know what else it could be besides pregnancy. Is the result of the pregnancy test accurate now?

Doctor's answer:

Hello; There are many reasons that can affect menstruation, such as
1. Mental stress
2. Work stress
3. Emotional stress
4. Depression or sadness
5. Taking birth control pills, weight-loss pills, etc.
6. Drinking strong tea, alcohol, smoking, or eating spicy foods
7. Exposure to cold
8. Singing loudly
Your factor may be due to fatigue from traveling and changes in the environment,
1. Pay attention to maintaining a happy and relaxed mood;
2. Adjust your diet to include more eggs, lean meat, fish, soy products, fresh vegetables, and fruits;
3. Increase nutrition, such as protein, vitamins, and iron, calcium, etc.;
4. Pay attention to, not staying up late;
5. During your period, pay attention to keeping warm, avoid getting cold, and do not get caught in the rain, wade in water, or swim. Do not sit in damp, shady places or near the vents of air conditioners or fans. Also, avoid taking cold showers or washing your feet with cold water to prevent menstrual disorders.