What Causes Short Term Memory Loss In A Marijuana Smoker?

Hi, i am 18 years old and ive been smoking marijuana on a casual basis, say 1-2 times a month, However sometimes i would smoke marijuana 3-4 times a week, but this isnt often. It has come to my attention that i am forgetting things occasionally such as keys, or misplacing something. I think i might have some damage due to smoking marijuana, is this reversible or will the memory lose symptoms go away?

Thank you