Guys:Why do men like challenge....................?

My bf is crazy. When I call him he answers my call but most of the time he tell me he is busy and will call me back later! I know he works 7 days a week. 70 hrs a week and thats A LOT. But we still manage to talk on the phone on his breaks. When he gets back home (at midnight) he says he wants to relax on tv and then calls me but I sometimes gets annoys as Idon'tt see him a lot and by the time he calls me back ill fall asleep. The thing is when I am busy or have no charge on my fone he calls me like crazy! leaving 20+ miss calls plus messages!!?? And when I call him back he says he was worried about me? Now when I call him he sometimesdon'tt pick upStraightt away so I feel like he is testing me or something so Idon'tt know how to reacttowardss this! I like been chased by him btw so how do I keep it without ruining the relationship?