I been feeling sick but not throwing up, pelvis pain, light head, back ache, not pooping, tired&a lot of discharge. my period isnt due until 3 days?

Could: Be premenstrual syndrome. If you have never felt this way before you could wait 3 days and if your period comes, likely premenstrual syndrome symptoms. If you are late for your period check a home pregnancy test. Ultimately the best advice would be to see your doctor for a complete history and physical with appropriate testing. Good luck.

See doctor: If you have had all these symptoms , it is time to see your doctor to get checked out.