Hey i am not sure if you are still on here but I have had the same problem. I used to suck my thumb when i was mad or sad as a sothing technique but soon developed into a habit I could not stop. Because you started at 6/7 something might have triggered it as around this age this isnt something you do unless you need to self south from a stressful life or had something else before (like a pacifier) I am not saying this is the case but if it is couselling may help.
Sucking your thumb is normal as a kid but when you grow older, ur right it becomes socially awkward espcially with peers or in public.
I know my parents did everything for me to stop (money, nail bitting solution) but I coudlnt.
What finally happen is if you suck your thumb while you develop into a teenager, the roof of your mouth forms around the shape of your thumb. I am not sure if this happened to you but it became a big problem. I finally stopped when a dentist put a cage in my mouth making it impossible to suck my thumb and my habit stopped, but then I had to crank my mouth open with a key in order to make my mouth the right size (as i have a small thumb) if this is still continuing it important to see your dentist, as they can help and it may have formed into a medical problem.
If you started at 6/7 you might be okay but i know your body is still developing and carrying this habit into teenage life would suck!!!
You just need to break the habit, find something else to use as a calming technique. I dont know, maybe a hugging a pillow, up to you.
Even like smoking you must break the habit and since that dentist put that awful cage in my mouth I have not even put my thumb in my mouth.
But if this problem is still contuning i would see a dentist for sure