>>6558164>>6558855>>6558919Honestly dude you'll have to just continue on with your life. Your mom has established that there won't be anything between you, holding out in hopes she gets tired of her BF and gets interested in you in very unhealthy, you are basically still viewing her an a romantic interest, despite her shutting you down.
I was in a very similar situation, loved my mother, confided in her, was turned down and she eventually found love. I was devastated at first but I got past it, she can love who she wants to love and I accepted that for her happiness and my mental state.
Maybe spend some time apart from her, or redefine your relationship, like keeping her at a distance/irregular contact. I don't know how close you are with your mom but I usually contact mine 2-3 times a month. Actually having physical time away from my mother really brought me out the depression, and allowed me to think about things in a stree-free environment.
The way I look at it is, if I can't have a relationship with my mother and fuck her whenever I want to, I'll at least make sure she's happy and I won't intrude on her personal life. I still love her, but I'm not crazy about it.