Last night I dumped by boyfriend who has cancer over text.
Is there a relationship between his cancer and your decision?
Yes, being around him when he's sick makes me feel sick, too.
It can be stressful to deal with someone that is going through a major illness. Abandoning someone because they have a serious illness and especially through text is very wrong, you should try to find ways to comfort your boyfriend while maintaining your own mental health. Simply abandoning someone with a serious illness will make people look down on you very negatively.
I didn't dump him online. I dumped him through text.
You don't need to stay with him forever just because he's sick, but it's cruel to dump someone in the middle of their treatments. At minimum you owe him the courtesy of a live conversation and not just a text.