I cheated on my boyfriend over 6 months ago and we are still together and he doesn't know
I'm concerned to hear about this. What caused you to end up cheating on him on him?
To get anger out on him
Being angry at another person can a hard thing to deal with. That being said, cheating is a breaking of trust and now you should come clean to him.
Nah, I like having him upset.
If you only want to be with him to make him upset, then both of you should examine the long term viability of the relationship.  I feel like if he loves you and if you love him back, you should make an effort to make him happy and not make him upset.