Based on your history, pregnancy is very unlikely. There was no ejaculation, condoms were used, and urine pregnancy tests done 20–21 days after intercourse and after missed periods being negative are reliable. A slight in periods can occur due to hormonal variation or a delayed ovulation, even without obvious stress or illness.
Next Steps
Can do a blood test to completely rule out pregnancy. If periods do not start in the next few days, a gynecologist may prescribe medication to induce withdrawal bleeding. You may also book an online consultation for further guidance.