i am assuming you are talking about strep in the throat (strep can occur in many other places). the reason may be simple: you are being exposed by someone who has strep or is an asymptomatic strep carrier. or you are the strep carrier and it doesn't completely resolve after your treatment (unless you have had a negative strep culture after you have been treated). the strep carrier could be your husband or just about anyone in your life including co-workers and friends.
i never had strep in 32 years until i got married 3 years ago. i have had it 5 times in 3 years. why?