y'know it's funny, sometimes I wonder the same thing. I haven't had a boyfriend in over a year and lately I seem like I lose my temper a lot or I'm just easily aggravated, especially when it comes to my family-they get it the worst. I don't mean to of course, but maybe it's because I'm not happy.
My best friend for my entire life, for a long time was always very cynical towards everyone and everything. Until she had her first boyfriend, like a year ago, I noticed a HUGE change in her attitude. She stopped trying to bring others down to make herself feel better I guess. After knowing her for so long though, I got used to the way she treated me and others and I just went along with it. Then, when she stopped acting that way, it was like she was a completely different person. I guess she was just finally happy, even though relationships are never perfect.
So I can't exactly answer your question, like if it's some type of withdrawal from not having sex, but it is a possibility. To tell you the truth, I've never been that into sex (kinda sad) so I wouldn't really know. I am trying to hold off sex until I'm married because I think sex can add stress to your life, just as being in a relationship can.
Hope that helped somehow ;)