Help please! Urgent!

TMI but someone please ease my mind and help me out here! I’m not too sure what this discharge is! I heard it gets yellow when exposed to air because normally it’s like a greyish white colour. It has a mild smell at first and sometimes can get a little musty or sweet smelling if it sits for too long. I am on birth control pills, my period should be coming in a week! Do you think I could be pregnant?