I realllllly need some help understanding the male species!!?

There's a guy i really like, he will be texting fine then i wont hear from him for a few days so ill text him & get a 1 word reply or sometimes nothing so i think he's really not interested (fair enough...im not desperate!) so i'll move on & try forget him, next thing he's coming to my work to see me...but why if he cant be bothered with me any other time? when i txt him he makes me feel like im a pain in the backside, i just really dont get it! can anyone enlighten me why he's blowing hot & cold?!!