Lol I know it's very confusing, but hopefully things will be cleared up in the next couple of chapters! Basically, Oliver does have romantic feelings for Natalie. But as we're starting to see (i.e. when Amanda came in and revealed the fact that she was with him the night before), he's not sure that he's ready to move on from Amanda. She showed back up in his life suddenly, and now he's second guessing his decision to let her go. And as for poor Natalie, she's left thinking that he never really had any feelings for her at all.