I slept in my mom's bed until I was 15
That's a little odd, why did you have to wait that long?
My mother made me feel safe and secure.
I'm sure you love your mother, but it's not normal to sleep in her bed when you are 15. You have to learn to be independent and care for yourself.
I am able to sleep in my mother's bed because my sisters can't.
If they are teenagers too, then they shouldn't be there in the first place. Teens need their privacy and independence, don't you want to have your own room to personalize and call your own? How about sleeping on your own once a week and increase it as time goes by to be independent?