in high schoo days I had a friend at church. = During my high school days, I had a friend in a church. And when I was about 20 years, I wanna to black out in front of the friend whom I have a crush on.= When I turned 20, I wanted to faint in front of this friend whom I had a crush on.
three of us including him was in the pub . after meeting he sent off me at home.  = After the meeting, he dropped me off home. although I intermittently blacked out , nothing happened to me.  =Although I often pass out, I didn't faint at all.  I had an unrequired love for him in my younger days. = I had an unrequitted love for him in my younger days.
Anyway, I have blacked out once since that time. I am not sure when...