Without hearing your mix it’s hard to help you but what I can tell you mastering a track is not as complex as it’s made out to be. Reverb, widening, compression/ or limiter. Though if your mix is bad your master track will never sound full. I try to keep my overrall volume as lloud as it can be without using a limiter or compressor but not exceeding over -.05 db and only when it sounds great mix wise and volume wise I apply my three trinkets of hope. Reverb widening compressor/limiter (I use L3-LL) if you release project with mutiple songs it’s a good idea to use the same process for all your songs.

Sometimes I get it right and sometimes I’m way off but when I’m way off it’s bexause of my poor mixing