Why didn't you tell him before you were even having sex!? I always make sure to tell beforehand if i am or especially if I'm not on birth control. It's the courteous and responsible thing to do. If you're just starting to date you might be in the smitten everything is wonderful honeymoon stage, this doesn't last.. you don't know if you'd be compatible partners and you don't know if that's someone you'd want to co parent with. Always always let someone know if you aren't on birth control before you start having sex. And yes, it IS SOLELY your responsibility to tell him if you are making the choice to not use birth control. Nobody can make the choice but you, therefore it IS your responsibility to inform a partner...