Is it normal to be bugged about my girlfriend having a lot of guy friends? I don't know why, but it really upsets me.
What you are feeling is called jealousy. John told us that there are three main categories of strong desire or lust in people: "For all that is in the world--the lust of the flesh, the lust of the eyes, and the pride of life--is not of the Father but is of the world" (I John 2:16). The pride of life is the desire to be liked and wanted by other people. It is a boast to your ego that your girlfriend wants you. But when you see that she has other guys as friends, you realize that you aren't quite as special as you thought you were. Thus, your pride gets in the way and you become jealous.
Reason should tell you that no one has limited friends. You have boys and girls whom you are friends with -- and so does she. She sees you as her boyfriend, which means she likes you better than the other guys she knows, but you are uncertain of your position and fear that another guy will take your place.
The truth is that such might happen, just as you might find another girl you are more interested in. That is why it is important in the early stages of getting to know someone that you don't over commit. You don't know what the future might hold and people, including you, might change their minds. So you let love develop at its own pace, not pushing it to speed it up. "I charge you, O daughters of Jerusalem, by the gazelles or by the does of the field, do not stir up nor awaken love until it pleases" (Song of Solmon 2:7). You tend to lose things when you rush things.