Can Orgametril prevent unwanted pregnancy?

I was prescribed Orgametril - 1 tablet from the 5th day to the 25th day of the cycle to inhibit ovulation for 6 months. This is not a typical contraceptive, so I'm afraid it will actually work like contraception and whether it will work from the first tablet. According to my gynecologist, he has less negative side effects (type thrombosis, breast pain, etc.). from typical contraceptives and at the same time adjust my period. Should I not be afraid of unwanted pregnancy .