I think my period went MIA.

Soooooooo I'm going to say this and I'm gonna have a lot of people envy my little issue but it's also very nerve racking. I haven't actually had a normal period without some sort of birth control in who knows how long. It started back in May of 2013, but still to this day I've probably had 4 period(that's being generous) without birth control and each one was normal. I talked to my doctor and they said it was normal for cycles to be off but to be completely gone? Nothing? Zip? That can't be normal. I haven't been on birth control for a while, my fiancé and I don't use protection and he's amazed that I'm not pregnant(can't have a baby if I don't menstrate). But how to I tell my doctor I need to figure out what's going on and get deeper into what's happening to my body that's causing me not to have a period? Has someone had an issue like this before and had some sort of answer? Help! :/