Originally Posted by justlost
Thus my fear... without his undivided love and loyalty... who am I?
I'm sensing here some significant degree of lack of self-esteem, and some long-lived and unresolved emotional "issues," as they are often called. I'd strongly recommend seeing a counselor / therapist and some diligent contemplative / mindfulness / meditative practice. You are not your role of mother or wife. You are a person, a human being, and your needs matter, and should matter to you.
Take baby steps, or big steps, but take steps to nurture and care for yourself and get to know yourself. Only when you care for yourself well can happy and healthy relationships with others naturally emerge. So this feels to me what you most need: self care, self-kindness, self-respect....
If need be, ask your partner to hold off on other relationships until your own is on a better footing. If he cannot or will not do that, you might want to let him go.