Just my thoughts of current 2 episode.. I cam see that I Sang trying so hard to have kid in current relationship and his previous one.. He may not trying hormonal therapy before, but he is now.. He inject himself with hormone (i saw that is FSH hormone that also help in production of testoterone and eventually sperm) .
Yes, denial and angry is a normal human reaction before came the realisation and accepting the condition.. For years HR dreams of being a mother. So its normal for her to react like that. She may notice I Sang struggle and hardwork to overcime his infertility when she read the list of ovulation induce agent that she didn't manage to read in episode 10.. Since she already saw the box of hormonal therapy on I Sang shelf, it will all click together.. HaRi is a smart girl..
ISang infertility may caused by hormonal disturbance that cause the production of sperm is low (or almost absent) as his sexual desire is potent. Thats why Dr Moon suggest he try hormone theraphy. Hormonal problem is the most rare causes of infertility in male.