Antara inj is just progesterone injection.it may cause amenorrhea,which is not of much worry.but sometimes it may cause intermenatrual spotting.but in your case ,irregular cycle is,may be due to stress,or hormonal imbalance.and white discharge may due to weakness.
Next Steps
consult a gynaecologist,for proper examination and tests to rule out other causes.
Health Tips
take fruits,green vegetables,milk and milk products in your diet.specially curd,which will increase your vaginal immunity.and help to control white discharge.