I think you should tell him (even though you don't have to), for your own sanity. The reason being that, if he truly loves you, it won't mean anything to him. You're still the same person you always were - and I think that he will see that.
However, if you hide this from him, there will always be a deep seated fear for the rest of your life that he will find out and react horribly. And the longer you wait, the harder it will be to tell him.
I think it would be good for your sanity to get that out of the way, so that your fears don't get in the way of your relationship.