Hello dear Understand your concern If you had done sexual intercourse in fertile period of cycle then there may be possibility of pregnancy. But I think i your case delayed period is due to Stress, change in life style, change in dietary habit, excessive loss of weight. So be relax, avoid stress and do not worry, gastritis is easily treated by prescribing mucaine gel and rantidine/omeprazole/esiniprazol tablet. Take healthy diet, fresh fruits and avoid spicy and oily food, take small frequent meal rather than large meal for gastritis treatment. Do exercise like walking and mediation for 45-60 minutes daily in the morning Period will come with in 5-6 days. If period will delay by 2 week and then you can go for home pregnancy kit to diagnose pregnancy. Hope this may help you Best regards Dr. Sagar