Naturally there is highest possibility of pregnancy
,if unprotected sexual intercourse is done with healthy woman around ovulation time in regular period.
Taking psychiatric medicine may cause hormonal
imbalance/hamper ovulation sometimes to interrupt pregnancy but it varies woman to woman. It also reduces the effectiveness of OCP/other pill.
So better to confirm pregnancy with blood test
after 1 wk of missed due date.
Practice safe sex by using safe period/Condom/Em Pill etc to avoid unwanted pregnancy.