I'm going to give my boyfriend an ultimatum
What will happen if your ultimatum doesn't get a positive response from your boyfriend?
I will still have to leave him.
We can't always get our way. Forcing your boyfriend to comply with your demands is controlling and manipulative. Don't try to dominate your boyfriend or he will leave you first.
It's his fault since he should be more understanding after all the things I've done for him.
It sounds like you're frustrated and fed up and you will end the relationship anyway. Just tell him how you feel and see where it goes.