Is it normal to suck my thumb?

so i'm 17 and I still suck my thumb, i've been doing it since I was a baby, not for periods, it's been constant, i've tried to stop doing it because my front teeth are looking bad and my thumb has like a ball but i can't help it, I mostly do it when im really comfy or bored, when im about to sleep or when i have really strong emotions like being frustrated or really sad, when i do it in those situations it's like a way to vent all my feelings, i do it when i'm alone or with my closest relatives, i remember doing it at school a few times but not intentionally i was distracted