My Heart is shattered. Why would he do this?! :( 10pts for advice and best a?

[calmbrain312]

So. I recently got out of a relationship with this guy. I'm 18, "goody two shoes" kinda girl. This guy who I met over Facebook who lives on the same town as me started talking to ne about 2 mo prior to our first meeting, came into my work to see me. My heart raced, I couldn't take my eyes off him. He felt the same. He said no one ever made him feel like that before. Time went on and we grew close. Now he's the "bad boy" smoking weed, rapper- with a very good voice, all that kinda stuff. He first lied about his age, told me he was 19, then 24. Then 25. Which is a big age difference. One day we got into a fight because I posted on his fb wall & he blocked me. One day he said his roomate found out I was young and claims he didn't know how he knew. Well I went back to our messages, read them crying cuz I take break ups hard. While going back to the messages, the next day., he had his profile pic of him kissing another girls cheek. We haven't talked since the day he told me his roomate found out. We were talking about marriage, he told me about a ring he was looking at 2 days before our break up. Someone explain to me what happend? He said obese perfect, not clingy, nor lazy, gave him space. He was gone a lot though. "helping his friends and fixing his car".. Why would a person lead someone on like that then just throw it all away..? I'm so heartbroken:,(