You really need to be open about it with your boyfriend if you expect the relationship to go anywhere. I understand the freaking out part, my wife freaked out when I told her that I didn't believe any more. Telling him might end the relationship depending on how strongly he believes, and if he buys into that "unevenly yoked" nonsense, but if that happens then it wasn't meant to be. It's up to your boyfriend to come to terms with whether he can accept your faithlessness, and if your other qualities are good enough to keep you as a girlfriend.
That's one reason I hate religion, because it divides people.
That's one reason I hate religion, because it divides people.
Christian apologetics is the art of rolling a dog turd in sugar and selling it as a donut.