How can your husband and Your Cousin's , Cousin have feelings? What should I do?

I moved my so called cousin in girls into my house last year. So goes in tell my husband a lot of lies about me cheating on him. Comes to found out they have been messing around behind my back. He had sex with her, now he wants to leave me. I'm so overwhelmed in losed. Stressed in can't eat at all. I ask him do you still want to be with me. His answer was well see. Wtf dose that mean. This lady is in her 40s wtf, it's going to started getting old being around a older person. Smh.