I hate lying

Today I was on the phone with my step mom and yelled at me daughter for jumping on the bed cause I wasn't feeling well. She asked if I was pregnant again, I lied and told her I wasn't. I don't want to lie to my family, but I'm not ready to tell them yet. I told my mom after my mmc not to ask me if I'm pregnant even if she thinks I am. I wish I had told everyone that. I'm on edge cause even at my last u/s and getting to see the babys heartbeat the doctor said not out of the woods just yet. Last time my baby stopped growing at 8w5d I'm currently 7w3d. My sister in law has a bday party that we plan to go to together which means I have to sit in the car with my dad and step mom for like an hour and a half. I'm worried they will ask again when they notice I'm not drinking at the party. I know I won't react well, and I certainly don't want to make a scene. Suggestions, I may just tell them I can't go, I hate bailing on everything.