Can I talk to my mother about this?
Yes you need to be honest about that kinda stuff
Yes, talk to her.
Yes, talk to your mom. 8 months is too soon to live with anyone, IMO, even young adults without kids. If they were smart they wouldn't be living together until they were seriously discussing marriage.
Of COURSE he is not who you think he is. But who he IS might be acceptable. It takes AT LEAST 2 years of being with someone before you start to see who they REALLY ae. Will he hurt you? Physically? Almost no chance of that. Will YOU hurt yourself, emotionally, if you get attached to him and then he and your mother break up? That depends on your cognitive self-statements and how you consciously allow yourself to respond to the situation. Talk to your mom about your fear. Just to get it off your chest but also so that she can understand any future fear-reactions you might exhibit. But don't expect it to change her decision. When it comes to other people's romances, you really have no control over that. Just relax and accept whatever this moment holds. That IS the only thing you CAN know. The future hasn't happened yet. And while we do need to prepare for the future (especially in matters of career, education and finances), we cannot LIVE in the future. And 90% of the things we fear turn out to never happen, so all we have done is make ourselves miserable over a fantasy. And when what we fear DOES happen, we are too busy dealing with it to be frightened by it. Like when you walk into a room where the floor is covered with marbles ..you are too busy working to stay upright to think "Omg .. what if I walk into a room of marbles?!!!!). Just live your life. Be as self-aware as possible at all times, and pay attention to the stories you are feeding into your brain AND to the emotions that arise FROM what you feed into your brain. We should never feed in "stories" that are false, but we need to be careful that we are not feeding our fear and suffering through the stories we select to go with.
Yes it is Ok for you to feel this way. Talk to Mom about it, if he was going to hurt you he probably would have already done it