Yes, it was his "moral obligation" to tell you if he knew he had herpes, but no, you cannot use his lack of conscientiousness to sue him.. there are some laws on the books in a number of states regarding intentional AIDS transmission but not herpes, which is not considered a "life threatening condition."
I hope at minimum you will always use a condom when engaging in sexual intercourse and know the history of future contacts - which may unfortunately mean asking them to be tested before you have oral or traditional sex.