How to get over my boyfriend abandoning me?

I'm 25, good-looking, well-educated and always try to make great efforts both at work and in life. I used to be stubborn, never fell blindly in love and would pull out of a relationship if my partner was not fit. But when I expected and treasured a relationship too much, all I got was pain.

Since I’m not young anymore, I started thinking of marriage and having a happy home when I entered this relationship. I’m obsessed with marriage because my two older sisters had broken marriages, which upset my parents. When I dated this guy, I expected to tie the knot with him. He was ambitious, smart, hard-working, and thought ahead although his family is not rich.

However, after a year of dating, he didn’t love me anymore. He hurt me many times by flirting with other girls, ignored me when I was sick, left me for months and then came back. My mind told me to end this toxic relationship. I reached out to my friends for advice but immediately ignored them when he tried to make me stay. I know I'm stupid but I still held onto it.

I've tried to save this relationship many times, even though I know that I deserved better. I’m stressed out about many things, from my career, to love and friendship. When someone leaves, I fall into the deepest state of depression. Grief makes me exhausted and I struggle to concentrate. A broken heart also affected my work.

I feel terrible right now. I can’t sleep or eat, and sometimes I’m drowning in negative thoughts. I can burst into tears at any time. I can't control my feelings. I don't know how to overcome this pain. I'm not brave enough to let things go, to live and work somewhere else.

How can I escape this painful situation? It’s suffocating me.