Theres alot of issues here mainly based on the required education of recording techniques.
But if your getting close to peaking and its still too quiet, then it probably means that certain elements of your mix are eating up the headroom or bandwidth of your song.
Its like this....
You have the low end of your kick drum, bass guitar and electric guitar all kranked up sounding super fat. You have all the guitars and vocals and cymbols EQ'd on the high end to sound super bright....
Now all your levels are way louder.
The entire mix is bright here and there and low end heavy, but there are holes everywhere that are lacking an over all balance.
Basically with time you will learn to be more subtle with use of EQ and volume.
You will need compression to bring your peaking instruments down to a level with the rest of the group so that in mastering you will bring everything up together.
All frequency's need to be represented to sound louder and fuller.
For the most part your mix needs to be close to flat but containing all of the solid elements it needs to sound good in a stereo which can later have additional bass mids and treble adjusted to the end listeners taste.
Heres a poor example.
Imagine your final Mix on a graphic equalizer or spectrum analizer.
Lows are peaking at -5, mids -10, highs at -5.
You raise the entire mix volume +5.
Now lows are peaking at 0, mids are peaking at -5 and highs are peaking at 0.
So the mids are still lacking making the mix quiet or empty because the lows and highs were eating up the headroom.
So you bring the highs and lows down -10 where the original mids were by using compression or removing excessive EQ'ing that was making it too bass heavy or to bright.
Now everything is balanced and you raise the entire level peaking at 0.
I would take some classes or by some books.
Modern Recording Techniques is a good book and colleges use it for their Recording Studio Techniques Classes.
Home Recording for Dummies will also help walk you through getting started quickly but I would just do as much research in recording and its going to suck for a long time until you start to learn by experience or start with the right information.