I think if I remeber right the cup is soft so you can sort of bend it...
Have you tried a small paper cup like a dixie cup?
Anything is worth a try...
Give him some time to adjust too! 6-8 weeks it might take.
IF your job is realy stressfull that might affect your pumping.
It might be ok for an older baby to go that long with out nurseing
Just expect them to want to nurse alot when you are together!