It could be Bacterial Vaginosis it has a fishy odor
Talk to a doctor if you are really concerned that something is wrong.
Also, though, consider that your odors are in the normal realm. Sometimes, using too much soap in that sensitive area, or wearing perfumed panty liners and so forth can actually make things worse. If you are clean, and you have no infections, then you probably will notice (especially if you are sensitive to odors) changes in both discharge and odor thoughout your menstrual cylce. I know that when I was young and all of this was new, I was very aware of the change, and self-conscious about it.
For the most part, I think that women are much more aware of and worried about this kind of thing than guys are. To them, you probably just smell like a girl, and that works for them!
I'd say that if you don't have any infections or other health problems going, then this is a thing not to get too worked up about.
Opus