Don't stay with someone just because you want to be with someone, and not specifically the person you are dating.
Ask yourself where you see the relationship going and if you really want to be with that person.
Do they make you happy? Do they add value to your life? Are you a better person because you are with them?
The bottom line is that you don't need a huge, glaring reason to break up with someone. If the only reason you are still with someone is because you don't see a reason not to be, then you should probably end it — for both of your sakes.
Being alone is better than being with someone you don't really care about, or who doesn't really care about you. It's OK to be alone for a while. Don't be afraid.
Besides, you are always less alone than you think.