Hi,
Excessive oil(sebum production ) is a prerequisite for the development of acne.This is regulated by androgens or male hormones.Androgen hormonal levels may be disturbed to some degree in female acne patients.However,this does not establish a causal link and at least a quarter of all cases remain unexplained.Sometimes, the hormonal levels may be abnormal,at other times ,levels are normal but the oil glands are hypersensitive to the hormones.Similarly,hair growth in a male pattern(thick hair on chin,beard area etc.)is also under the influence of male hormones.Androgen effects on the sebaceous glands are reasonably well characterised but the variability in response is not fully understood.Other factors may also be involved in determining this suscepibility and may be varying from time to time.This may be the reason for the good response to anti -androgen medications(OCP and spironolactone) initially and poor response thereafter.
Acne,excess facial hair and oiliness can occur as part of a syndrome called polycystic ovarian syndrome(PCOS). It is usually seen in young obese females with menstual irregularities.You can get your PCOS profile done(testosterone,SHBG,androstenedione,DHEA,Prolactin ,FSH,LH) and see if there is any gross abnormality in hormonal levels.
Other reasons for non responsiveness to anti acne mediations include antibiotic resistance,gram negative folliculitis etc.(your physician would be able to address these).Isotretinoin is definitely a good option for you.
Hope,I could clarify your doubts at least a little bit.If you have any more queries or require any more clarifications,feel free to get back to me.

Regards,
Dr.Veena Chandran