His step-mother

Okay, so my boyfriends family is all very Catholic, I'm Christian and have my own beliefs, much different than them. He told his father 6 weeks ago that I was pregnant(now 12w4). His father was nervous to tell the step mother due to the fact her daughter has been trying to convince for two years. We were uninvited to thanksgiving because she didn't want us to "offend" anybody. Now they are wanting to meet for dinner this Thursday and we both have a feeling it's going to be about Christmas. I'm so hurt. This is the first grandchild for both of our families. My family is so excited and can't wait, even flying from CA to be here for birth. I know that another big part of all of this is that we aren't married, which I think is utter nonsense. I don't know what to say or think. He wants me to keep my thoughts to myself and not lose it when I see them, which I will be respectful... but I'm really hurt. I feel like the life of this child doesn't matter, all because the step sister is having trouble getting pregnant....