mother in law ( basically ) problems

So me and my SO have been dating for 2 years. Today we decided to get a phone plan together, we did.(( we already talked about what would happen if we broke up, so DONT bring it up we talked about it )) He told his mom and his mom FREAKED out on him. She cussed him out and blamed me and now I'm freaking out and having a panic attack. Idk what to do my boyfriend says it's fine but I feel like he's upset and disappointed. I feel like I talked to him and made him join. Idk I'm over thinking it but I started to cry and freak out because I HATE when people's parents are mad at me.