It was feeling drafty in my house. More than usual. I went in my bedroom and the whole bottom sash of my window had fallen out. It was still connected but completely open. I shut it but an hour later the wind pushed it back open again. It's going to be in the thirties tonight and I have no idea what to do. I've googled it but haven't found anything matching my problem. Also, the other night when I went to close said window, it gave me a hard time and came off the tracks then too and this time a little slanted white piece of plastic popped out and I have no idea where it came from. I've looked around and think I know exactly where it came from but don't know how to get it back in. I've tried to pop the whole sash out to get a closer look but it won't budge and isn't easy to remove like the tutorials on Youtube say it is. Maybe because it's an older window??? Pics included. Excuse the screen holes courtesy of my cat...

I would really appreciate any help.

-Tammy