Clingy baby

Last few days baby boy is crying all day long, actually not really crying, more like whining. Nothing i do can calm him. Also he refuse to take a nap, he crys and i can tell he is so sleepy and it takes me ages untill he falls asleep and then he naps for half an hour tops. He is not hungry or wet. I do think he is teething at the moment, his upper teeth are about to pop. Is this cause of teeth or is it a phase? Anyone else going through this?