I appreciate your query.
Based on the date of your last menstrual period, you had sexual relationship around the days of your ovulation. Also , since you are not sure, and your private parts were in contact, pregnancy
cannot be totally ruled out.
Antibiotics and antacids ( which you have taken ) generally do not delay period.
The only way to confirm your situation is by taking a home ( HCG
) urine pregnancy test kit.
It makes sense to do that at the earliest, because even if by chance you have conceived, you can go in for medical termination, if you detect it early.
Please do not put off doing this any longer.
Also, before panicking, remember, that in absence of penetrative sex, the chances of pregnancy are minute, but you need to rule it out before proceeding further.
All the best.