Overbearing, cautious or just in love?

I know sometimes I get clingy or moody or jealous. But what's a girl to do when her relationships never last past 6-7 months?
Tyler and I have been doing good and we've been together almost 7 months, so a part of me is extremely scared.
I know this part is going to be a huge hurdle for me to get over. I'm scared I'm not going to be enough for him. That he'll get bored with having me as his girlfriend and will leave just like that. He doesn't know I'm scared about  going out of state for a week, and I'm honestly kind of scared to tell him.
I'm scared he might not be here when I get back... or that he'll do something and won't tell me.
The truth is, I'm just scared. Scared of getting hurt, getting my heart broken again, scared that I might actually have a real relationship finally.

But how do I go about telling him? Should I even bother or should I just keep it to myself?  Why is this so complicated for me.