David E,
I have experienced similar symptoms as you, although I think mine have "progressed" further than yours at this point. I am also 48 years old... About 12 years ago, doctors noticed during a routine CBC that my counts were low... not dangerously low, but "out of range" low in all the major blood lines -- RBC, WBC, and platelets.
I think when we started regularly monitoring my blood, my platelets were in the 120-130 range. They have gradually dropped over 12 years to 34 at last reading about a month ago. My other blood lines have also dropped some, but perhaps the droppage is not as dramatically seen as in the platelets.
Like you, I still have no (or few) symptoms. At this point, I have had no bruising, bleeding, or infections -- I am thankful to God every day for this! My hemaglobin is below normal as well (was 10.0 at last reading), and this affects my endurance at times, but overall, I feel pretty good and push myself to stay active. Of course, I know others with platelets higher than mine who are experiencing problems -- everyone is different in how they respond to all this. I also have not had to go on any treatment (yet)... no transfusions, no ATG, no BMT... it looks like I am slowy trending that way -- but we'll burn that bridge when we come to it!
I'm sure you are wondering if your "trends" are going to gradually lead you to where I am, and beyond... In your case, it sounds like you really need more data. I'm pretty sure a BMB is in your future...
From what I have read, cases like mine (and possibly yours) where blood counts drop extremely slowly over time are not the "norm" for AA or MDS -- but they do occasionally happen and they are certainly involve bone marrow failure. My doctors have hesitated to label my condition as AA -- they refer to it as pancytopenia. I am still learning, as most of us are, and this web site is a rich repository of information. There are people on this forum who can help you!
Keep us updated on your condition!
David M