How to determine correct level of Wave form?

[ihate100bees]

In preferences (metering), I chose a Digital VU. My low color break point is -20 and my high color break is -6. Also O = O. Everything is set for 48k recording and mixed thru my Sony DMX R100 console at 48k. My mixes are perfectly aligned within these numbers. From my Sony mix buss I run the mix thru 2 outboard compressors, then back into PT to a stereo track... again the levels look and sound perfectly clear...but when I do a "bounce" to a mp3 set to 320 and drop it onto a flash drive to play in my car... it's very low compared to everything else I hear that has been mastered... or other friends that work with music. Am I wrong to mix less at these levels? I understand and know about levels required for pre mastering but still... with everyone using software in their houses now to "Master"... mine is much lower. Also in comparing the height of MY wave forms, they are just under the top. If I zoom in, they increase. Is there a "default" setting to be sure I am not on a zoomed in wave form setting? When I import a mix from someone else and compare it, the top of the Wave form is smashed, compared to mine. Ideas? thanks!