Blacked out after being fingered

My bf and I were getting eachother off in the bathroom. We were both standing and he fingered me. After awhile I started feeling light headed and all I remember was telling him that until I blacked out. I felt like I was asleep napping. Then all of a sudden I see my boyfriend appear in my vision calling my name. He told me I fell in his arms and my eyes were open the entire time. And I did a little twitch as if I was sleeping. This only lasted a few seconds according to him but after he lifted my head I woke up. What happened to me?

Recently I took plan b but that was over two weeks ago and I've just finished my period.