One of the goals of producing a contact sheet is to see which of your exposures are ok, and which aren't. If you don't have consistent exposures in your film, ie. some over and some under exposed, you won't get an even contact sheet.
When I print a contact sheet I find the time necessary to get maximum black from the paper in the unexposed film, and then expose the paper at grade 2.5 (difusion enlarger).
If you get a very dark overall result, this will tell you that all photos were under exposed, and vice versa.
If, like you, I get lots of too dark and too white photos, this will tell my I was failing in calculating the exposure of my photos.
How are you mettering light? spot, center weight, auto, matrix?
If you want you can give each frame a different exposure time, but this is a lot of work and not the goal of a contact sheet.