I have a really really bad memory

Sometimes when I need to/want to remember something I just black out..and this happens all the time..I see myself as a fairly educated person but at times I can't even remember how to sleep a simple word like 'the' or remember the alphabet..I hate this and it always happens!!! For instance if I'm taking a test and need to remember 1*1 I can't even remember that..I will sit there thinking for about 15min till I can get it

and sometimes when I place items somewhere after 2min I can't remember where it is..also when I say something or somebody else tells me something I don't remember it at all..

I try really hard to remember things sometimes I do but most of the time I'm just stuck blank..black in my mind nothing there..sometimes I don't remember the year of my birthday either..I often answer questions with I don't know because I really can't remember..I'm not trying to act dumb..it's just I dunno..

this needs to stop because it really really gets on my nerves..aaah sorry for complaining