I don't know what to do???

So I have had this "thing" with a guy for a while now Jakub he is 17 I am 16. We have had sex quite a lot of times, but none of our families know anything about us.

So a few days ago my mum came up to me and my brother and sister and said there was someone she would like us to meet. As in like a guy she was dating, we were all super happy for her because my Dad passed a way a few years ago and it has been quite hard on her.

ANYWAY fast forward to this morning, we pulled up outside the restaurant to meet this guy, we go in and I see Jakubs dad sitting at an empty table. My mind doesn't pick up on this until Mum leads us over there and starts introducing us to him as her boyfriend. I try not to act shocked and just play along with being all sweet.

I manage to get away from the table and go to the bathroom where I called Jakub and told him our parents are dating, he didn't believe it so I sent him a pic of them together.

We don't know what to do, do we tell them or keep it a secret and see how it turns out?