我要上班--
1、 I will go to work.
一会儿我要上班。(I will go to work later)
2、 I want to go to work.
我待在家里的时间够长了,我要上班。 (I stay at home too long enough, I want to go to work.
3、I have to go to work.
今天我要上班,不能和你出去了。(I have to go to work today, can not hang out with you.)
我得上班--
I must (have to) go to work.
不能再待下去了,我得上班了。(Can't stay any longer, I must go to work.)
"得" is stronger than "要" in this case.
Hope can help you :)