What to do when baby has a cold?

My 9 week old has always been congested but just yesterday afternoon she's been sneezing more often and coughing that mucus cough/sore throat that you get when you have a cold and a bit fussy last night. Her temperature was higher then her normal temp yesterday 98.9 but still in the normal temperature range and eventually it went back down to 98.3. I read somewhere that if they're younger then 3 months to take them to the e.r but she sees her doctor Monday morning for her 2 month check so I'm not sure if I should wait or go?