Get rid of dog?

I’m in tears trying to even write this.. I have a 1 year old Rottweiler. & he is so sweet, and usually at all times when my fiancé is home he is the perfect angel... recently he has been kind of aggressive and attacking me somewhat. But today, he did it and it wasn’t horrible, and then just a second ago I went to pet him and he straight attacked me. I mean I’m lucky I’m not laying out on the floor... I had to hit him to get him to stop, and then he kind of turned normal... all I seen was his vicious face and all I can feel is how his teeth were like locked into my arm and he scratched my pregnant stomach and all... I’m so shook up about it. & at this point I think we might have to get rid of him. Fiance is at work, and I could of been here possible really injured with no help whatsoever and it’s really got me scared. I have the dog locked away... but I’m so upset and can’t stop crying. I just don’t know what do do. I almost want to leave and go to my moms.