Cubase 5 Export Sounds Different Than Playback Inside Cubase

Hello all,
I am using a version of Cubase 5 and I am running into a very annoying problem that I can’t figure out. When i try to export my project, it sounds very different than how it sounds inside Cubase. I recorded all the audio files with a Focusrite Scarlett 2i2 audio interface, and when I listen to the playback inside Cubase through this interface the project sounds as it should. When exported, the mp3 file sounds the same as inside Cubase only when I listen to it through my audio interface. If I disconnect the interface and listen directly through the headphone jack of my computer the audio sounds muffled and some of the recorded tracks are barely audible. The same thing happens when I listen to the file on my phone for example. I’m not sure if this is a problem with the actual export because the project sounds the same exactly as inside Cubase but only when I use the interface that I use inside Cubase. I have tried a few file types and different settings with the export but all of it comes out sounding the same.
Does anyone know where the issue could be?

Hi and welcome,

Do you compare at the same sound system? Or do you compare the record on different speaker(s)/headphones?

If the 2nd is the case, then you should learn about the art of Mixing and Mastering.