Why am i not getting bigger?

heres my workout schedule, 2 kids of days when i workout, day 1 is arms ams and shoulders, day 2 is chest and back, so iv been working out for 3 months, i switch up my workout routine every 2 weeks so my muscles dont get used to the excercise, so i workout every muscle group intensly for half an hourm so pretty much i workout for an hour a day, when i am done i drink my protein shake thouout the day, so pretty much my one time free personal trainer at bally told me to do all this and i have been but i dont see any reults, is there something im doing wrong??