What could be making me cry very very easily?

Okay so I am a very empathetic person, and I really love people and helping others. I wouldn't say that I'm a cry baby, but I cry often . Not like balling over something for hours, more like sheding a tear when I we something that will make me feel empathetic. Like If I see a commercial and there's a person that's hurting and needs help, I feel like through their eyes I can see their pain and it sucks that i can't do anything about it. I shed tears often because I see situations like this everyday. But today for some reason I actually cried . I cried over commercials. I watched a music video. A song . Watching "Radio", watching "Front Of The Cl".And I usually am concious of what I'm feeling and if I'm going to cry but at times today I couldn't control it . What can be doing this to me? Like what changes can be causing me to be so sensitive and emotional? Don't say period or drugs.I kept shedding tears that my eyes and cheeks hurt from all the wiping. LOL.any polite and not immature answers would help. Thanks.