I had some similar difficulties with my memory as a child and as an adult but I always tested well so it didn't look like I had a problem. I could almost always focus really well while taking a test for some reason.
The problem that I had was something that is probably not considered a learning disability but I felt that it affected my ability to learn and function in life. I had the good brain days where things clicked easily and then those days where I must have been operating on autopilot and I wasn't paying attention to things going on around me and I had difficulty concentrating on anything. I learned to take a lot of notes just in case something didn't stick in my brain. One of the reasons I was so worried about my son's difficulty with handwriting was that I relied on my notetaking ability so much.
My problem was anxiety. I didn't even to be actively worrying about something for it to affect me. Thoughts and fortunately sometimes solutions would often just pop in my head when I tried to focus on other things. I wondered at those times if I had some kind of anxiety induced ADD. It was something I had to learn to live with.