Those questions you have? Whether he's the one, whether you feel about him the way you should, or whether the relationship is going okay? When you're not sure whether you're in love with someone or not, the answer is not.
Rejection, though--it could make the loss of someone you weren't even that crazy about feel gut wrenching and world ending.
And pity--people who inspire it in you are actually very powerful people. To get someone else to take care of you, to feel sorry for you--that takes a lot of strength, smarts, manipulation. Very powerful people.
The loneliness you feel with another person, the wrong person, is the loneliest of all.