Suggestions about my relationship?

I've been going out with this girl I especially like for three months next week. We started off HOT, but everything's been kind of dulling down lately. We don't talk nearly as much, and when we make love, it is not nearly as pionate as it used to be. I'm not sure if this just means she or I need a break, or if our relationship is on the brink. Could someone please give me some advice?