What about Fear of water? Phobias: xenophobia definition is a bit simplistic; yes 'strangers' but also more towards the fear of foreigners. Usually, used socially and culturally than just 'strangers' but I digress.
It's not just about sex. Don't get me wrong sex is fucking great. But, when you have a connection with someone, when you feel so strong for someone. Just a kiss is enough to make your knees weak. You just can't beat that.