Is it ok to take medicine if you don't know your pregnant? will it affect anything?

Not absolutely safe.: It depends on the medicine. Some medications are clearly not to be taken during pregnancy. Some not in early pregnancy. So it matters. Go find out if your pregnant. If negative, it's not an issue.

Assume you are: When pregnancy is possible but unknown, it is best to treat your body as if you are. Check labels for safety during pregnancy, don't drink alcohol, take your vitamins and avoid fumes and other caustic substances, just to be on the safe (and responsible side).