If it's only been a few dates, then I see no reason to disclose it. However, if you continue working while the relationship developes, you sorta owe it to him to be honest about how you're earning money.

When you say that you're going to finish the year, I'm not sure if you mean until the end of 2014, or if you mean a year after this relationship has started? If you mean until the end of 2014 then yeah, that's reasonable as it gives you a few months of getting to know each other - that said, you'd be 4 months into your relationship. I've just hit 5 months with mine, and I can't imagine witholding such a big thing from him.

If you stop working, I see no harm in telling him that you have been an escort in the past and that you're no longer doing so - and that would be totally fair to not share with him until whenever you see fit.

It just changes if you continue working throughout the relationship, because he deserves to know that your relationship isn't sexually exclusive and that he needs to be extra careful about STDs, as do you.