Why? I will tell you why. I cant speak for everyone but I have been their. Trust me it is not easy. But there is a light at the end of this dark and dismal road. You will always have people that care about you. Your mother is to caught up in her own life to realize what she is doing and she will see it one day and regret it. She may not say anything to you but she will feel guilty about it. As far as your ex just cut all ties with him and do not feed into his shenanigans.
You are a very pretty girl and will find find that someone special, but do not jump into anything to fast. Give your self sometime to adapt to your new surroundings.
Now go and pick up your favorite snake and go sit in your favorite chair and just veg out.
If you need to talk you know where to find some great people that care about you.
Take care of YOURSELF!