Honestly, you need to be blunt with them. Tell them you want a family meeting, and you want them to be quiet while you talk. Take turns explaining what's good/bad about what's going on. Don't stop if someone starts crying - continue on and explain how you feel and why you're not comfortable with the situation. If you don't want another man in your house yet, and your mother ends up taking his side, don't be afraid to tell her that it's a disgrace that she's putting her romantical interests ahead of her own children.
Sometimes, you just have to be hard with your parents to get them to understand.
>>2 School counselors should have nothing to do with your life. Bringing an outsider into a situation like this, especially, would make it a lot more unnecessarily complex.