My 5 month old has cough and chest congestion and spits up mucus she's had this for 4 days should i take her in to dr?

Yes: Even though most likely she has a cold...If she has had congestion and cough for 4 days at this age, better for your pediatrician to listen and be sure all is well.

I would: Yes that would be a good idea to do a complete head to toe exam. I have examined children with vague symptoms to find they have an ear infection or something very treatable. Good luck please see your physician.