Why does the idea of sex repulse me all of a sudden?

Patient: Hi I am 20 years old and should have a high sex drive however for the past 7 months or so the thought of sex is just so unappealing to me. I used to be very sexually active. My boyfriend gave me genital herpes 6 months into our relationship however our sex drive remained high. I am 4 months pregnant now and I never want to have sex or perform any sexual acts. My boyfriend is always asking whats wrong, so I still want to be with him, I should be wanting to have sex with him etc. I love him and want to be with him sex just feels uncomfortable and the thought disgusts me. Also the more he begs I will do it just to please him and then I will feel I upset afterwards and resent him. What is wrong with me?