What do you mean you don't have me in your life?

"I am missing in your life" and "I am missing you in my life" mean:

1. You don't need me in your life: this is a joke or a teasing statement, which shows that you are very important to each other, need mutual support, or express your concern that you are not independent enough.

2. I lack you in my life: this is a romantic expression, which means that I need each other very much and hope to be with each other to express my deep love.

No matter what kind of expression, it needs to be understood according to the specific context and situation.