What Causes Persistent White Vaginal Discharge?

Is there something wrong that I ve been having a white discharge since I was 19 and I been had plenty of shots because I kept thinking I had some type of std , but after I still was having discharge. I get wet for no reason it s not creamy. But when I drys up it gets crusty and stuck to my panties. I bee having this going on for so long and I have had shots. But still nothing s changed. It didn t do it while I was pregnant and every time they checked I didn t have anything . I just had my baby last year.