How do I ask him to pay for plan b?

So my bf and I had a little mishap with the condom, and it's been at least two days and I've been feeling weird cramps in my stomach. He said he didn't finish, but I'm still super paranoid. I want to take a plan b but I don't have any money for it, and my local clinic is only allowing me to schedule it two weeks in advance!? (I know crazy right) how should I approach him to ask for it?