Thank you for your query.
The pinkish discharge could be premenstrual spotting.
Causes include endometriosis
, endometrial polyps, cervical lesions, fibroids etc.
Since you also have fishy smell and vulval tenderness, it points towards an infection or a cervical polyp
Infections could be other than thrush, and fishy smell is mostly associated with Bacterial Vaginosis
( BV ).
I would ask you to consult a gynecologist, and have complete evaluation of your cervix and uterus.
Also, a high vaginal swab
and screen for pelvic infections.
The birth control also sometimes causes erratic spotting.