What Causes Vaginal Discharge During Pregnancy?

hi 30 years old pregnant of 24 weeks , have clear vaginal discharge for 3 weeks with very avid taste , like lemon , light smell but nothing nasty just different than usual , at first only clear discharge than , got some small white part , did a 3 days yeast infections treatment to eliminate this possibility everthing seem back to normal for a week and now it is back again , the clear acid bitter taste discharge but no small part in it. no itching or burning occur what so ever. Thank you