Why can't I leave my bf?

My boyfriend is very controlling, he hates it when I go see anyone including friends and family. He makes comments on the way I look and what I do and eat constantly.

He doesn't want me to have my own life, he wants me to solely rely on him financially so I have no independence whatsoever.

It's so so hard to leave, I feel like such a doormat. He provides for me and I wouldn't be able to sustain myself unless I go and get this degree he desperately doesn't want me to get. I'm sure he is cheating on me, he always has secret phone and secret dating profiles online even though I have never cheated.

Jesus Christ just why can't I leave him? I'm so scared of starting a new life on my own. I'm to embarrassed to talk about this with my family, I've always started strong for them.

I just need some strength and a clear head. I need to go study to find a better life and a good job that I love.

Had anyone else been in this position? I thought this would be a good life - a life without financial worries. Comes with a catch.