My 1yrs old ferret?

my boy ferret is about 1yrs old i think, and well i got him and a girl 4days ago...the boy just sits around doin nuthing.but i think hes sick or has problems. when i let him out for his cage...he doesnt walk like the femal does.he walks with his body straight and doesnt slouch. hes just doesnt look right.also when i let him out he walks for a few steps then just lays down for a few seconds. then he gets back up and walks a few steps and does it again. he does it all the time and alot.he never realy wants to play. sometimes he plays with the girl but not for a long time. then he just sleeps i dont know whats wrong with him but i would rely like to know. and when i also try to play with him he sometimes terns his head around and looks at my hand like he wants to bite me or sumtin! i dont know please help???