lost my virginity Sunday morning

so last Sunday I lost my v card it hurt a little bit when it went in then he went to town and it felt soooo good the only thing is that when I stood up I almost passed out and was very dizzy I told him I was fine we went about our day then waited a few days b4 doing it again which was around 3 am this morning we did anal then vaginal it felt really good hurt at first but I was fine and fell asleep so what could be the cause of me almost passing out