I think my dad is using meth. can you help me what are some signs and does his match up?

My dad is dating someone she was once in rehab for doing meth now she is out. Im afraid that she has got my dad hooked on it. My dad works 2 jobs and gets paid over 1,000 dollars every 2 weeks its only him he doesn’t pay anything but rent but he seems to be always out of money. So i went over his house to get my game the other day and i walked inside the house and his girlfriend came out she kept hugging me but at the same time she was pushing me out of the house then she told me that they had sold my game when my dad had been telling me that it was in his car. When my mom yelled where my game was he got so angry in a way we have never seen him he looked violent and he yelled and he got emotional and we have never seen or heard him curse toward our mom the way he did she’d never seen it before neither. Then when we looked we saw a black male in the door and a white male in the backyard we have never seen before. He has also lost a lot of weight. i really dont know what is going on CAN YOU TELL ME THE SIGNS OF SOMEONE USING METH? and is this a possibility that he could?