Do I have a problem with commitment and being in relationships or am I meant to be single?

I've only ever had two "boyfriends" and I quoted that because the first one only lasted 2 weeks and all we did was kiss, we didn't really go out like boyfriend and girlfriend. I really liked him at first but after two weeks I started losing interest and didn't want to hang out with him anymore. I made up excuses if he wanted to hang out, saying I had homework or I was just too busy. I've since broken up with that guy. Now, I'm with another guy and he asked me if I wanted to be his girlfriend and I said yes. Thing is, I'm already starting to feel like I want separation. What should I do in this situation?

Am I just meant to be single?? I feel like I lose interest so quickly that relationships aren't even worth it..