If, as you say, you don't press hard when writing, a normal 0.5mm pencil may suit you - if darkness/clarity of lines is an issue, you could try different lead densities - "B" for example is slightly less-dense / draws-darker-lines than "HB" (which is approx. equiv. to the familiar standard "#2"), or you might prefer "2B", "3B", or etc.
Another thought is ultra-fine-felt-tip artist markers. I know there is a full line by Staedtler, down to at least 0.3mm. You should be able to find a good variety at any decent-sized art-supply store. A felt-tip pen avoids all the drawbacks you cite, and, in my experience, draws a line as consistent as the pressure you write it with.
Personally, I use 0.9mm mech.pencils for everything (except legal docs). I'm not aware that there's a difference in drawn thickness - as opposed to the more common 0.5 or 0.7mm units (or, no difference that can't be moderated by attack pressure). As a bonus the 0.9mm leads don't constantly break under your hand.