I'm in a similar situation, and am leaning toward it being a circulation issue. Would you happen to know what your last blood pressure measurements were?

My previous lead candidate was proto-diabetes, but the most recent tests suggest otherwise. The only comment made about my bloodpressure was by the trainee EMT, saying "I wish my bloodpressure was that low!". I've been suspicious that the safe range for bloodpressure might be shifted a bit too far downward, since most people suffer from high bloodpressure-related conditions, but I'll need to refind the evidence that pushed me in that direction.

Anyway, my current strategy is to try and get more/better exercise, fresh air and sunlight. Those are good ideas in general, and should have an impact if it's circulation-related. It's too early and I'm still struggling to get good exercise, and I didn't think to try and quantify changes until... just now, so right now, this solution is experimental on my end.