You’re relying on the limiter for loudness. Loudness comes from multiple stages in a mix. Believe it or not, a lot of loudness is achieved from CUTTING frequencies, not boosting them. You’re not able to go any louder because you’re boosting stuff you don’t need at the end of your mix, therefore you’re not able to push the limiter as hard without clipping.
Another secret is which frequencies you should be cutting. Everyone always assumes you have to high pass everything except the bass elements, which helps, but what people don’t realize is there are frequencies at the top end that need to be cut as well. I remember it took forever for soundclick producers to realize this. Everyone’s mixes sounded like they only knew to high pass everything during the days of Johnny Juliano and Superstar O. Gotta cut those unnecessary highs as well. From there you can compress the individual sounds and boost them up. THEN you can take the mix to the limiting stage and really crank that sucker. Otherwise you’re capping your space because your mix is too full.
It’s all about taking out what you don’t need and keeping what is important. And remember it’s not how the individual elements sound on their own. It’s how it all sounds together in the mix.
Some will tell you some crap like “Oh, well it’s because they are using better hardware equipment than your software.” which to an extent is true, but it’s definitely possible to get as loud without it and keep quality if you mix properly at each stage.
Also, check out TT Dynamic meter. It will actually measure perceived loudness (What our ears tell us is actually loud) rather than a basic db meter that shows the peak. Grab a reference track of some mastered tracks and check out their dynamic range compared to yours. That will help give you a guideline of what you’re actually trying to achieve rather than just looking at a number that says it’s peaking at -3db…that means almost nothing in terms of what you’re trying to do. You want actual perceived loudness (what our ears actually tell is loud or not).