I'm not going to do anything for my sos birthday
Why aren't you doing anything for their birthday?
I just don't feel like doing anything.
You should at least get them something special. Not doing anything at all shows how much you value you them.
I don't know if I like him enough to do it.
I just think it's hurtful that you won't even do anything for your partner's birthday. I think you're going to make him really sad.