"I also had someone telling me that my voice sounded a bit bathroomy?" What Gecko mentioned is likely--the reverb on your voice. As he suggested, try a "bigger" reverb, like say a Cathedral or church reverb, and keep it down in the mix. Use a send/return for it. You might also want to put a delay on it. Something subtle, matched to the tempo. I routinely do this on vocals. One send to the reverb, another to the delay. Both effects get their own AUX return. I use a ping-pong delay, mixed way down so you can just hear it, no more than two or three "pings" back and forth. That is a subjective thing, just like any reverb or delay. I've heard mixes by other people where the ping-pong is too pronounced, too much left-right-left-right that is too loud. It also doesn't have to ping; try different delays set to different lengths too. It's something worth experimenting on. The biggest thing though to me still is the stereo spread. Widen the field by placing the guitars more in a left-right position. By using delays and reverb this can be enhanced, not just with the panned guitars, but with the vocals and keyboards. In other words, delay and reverb are working with the panning assignments. It's impossible to explain exactly, but I think you'll begin to figure it out.
I would always record with WAVs, at at least 48kHz and of course 24 bits. I suppose 44.1 sample rate is okay too, and of course on up to 96kHz. And what CrowsofFritz mentioned about 320kbps. There is no reason not to bounce down to the highest resolution Mp3. Also, I was assuming you mixed the song in a room, hence my belief that you couldn't hear properly what was going on--the room in which you listen to the tracks whilst mixing is very important. That's what I meant by saying your room added some "color." You couldn't hear it, but the room ultimately had an affect on the mix. Even if you record your guitars and bass directly in through the interface, the room in which you're listening back to those mixed instruments in will have you making bad decisions with EQ and effects, panning, levels of individual tracks, etc. You could and should check the mix on headphones, or even mix on 'phones, assuming you have some good ones.
