I know scales are not a necessary expense, but if its bothering you that much maybe you can suck it up and get a new one? A scale should be able to at least keep your weight accurate to within a pound or two, ten seems excessive. Overstock.com has some scales right now that seem to have good reviews for as low as 30 bucks, I think I got my scale at walmart for under 20 bucks and it seems to do a decent job, it does move up and down based on what I'm wearing anyway, I'm sure if I was carrying weights it'd register that! You might even check ebay or craigslist for a used scale to save some cash. As annoying as scales can be with all their variance, it is an easy way to keep track of your progress. I take all my readings with a grain of salt, but I do like to keep tabs on it just the same
If all else fails do you have a friend with a scale you can visit time to time to check yourself?