I Have an Overactive Sex Drive?!? Help. >.< 10pts?

I'm a girl, 21, and a virgin. I've never had a bf, dated or anything, but I think about sex constantly, and have always had a big sexual appetite. I masturbate most nights, watch porn, etc. Last night I actually was able to make myself come 3 times, but it took awhile. Unfortunately, even after all that, I was still horny, just too tired and sore to continue. It's all outside stimulation btw. Does anyone else feel like this on the regular? Is it bad? Can loneliness or depression cause this? I feel both ways more than I care to admit. All mature answers please. Thanx!