Why has it been taking longer for me to have an orgasm than usual?

Me and my boy friend spent three days together, and he was always fingering me and playing with my clit. At first, it didn't take me very long to "get off", only a couple minutes and it happened multiple times. On the second night it started happening after a longer period of time and it only happened once, twice if I was lucky. I'm wondering what could cause this to happen and if there's something I could do about it?