I have a cold? a sign of pregnancy? have any women had a cold before their expected period?

i'm supposed to get my period thursday or friday and i've heard that some pregnant get colds during early pregnancy because their immune system lowers so it wont fight off the baby. this morning i woke up feeling stuffy and groggy and extremely exhausted. could this be a sign that this is the month? have you had a cold then turned out to be pregnant?