Yeah Shep, a few months ago, i used to die on easy. ttfaf/slayer
I went in this order
Easy all 3 or 4stars, a few five stars then half of medium
back to easy to five star every level
finished off medium 3 or 4 stars, a few 5's again, then got through half of hard mode,
went back and 5starred all of medium apart from ttfaf
completed hard mode all 3 or 4stars a few 5's again... then completed half of expert, etc.etc.etc.etc.
You should see steasy improvement as you start hard mode though, you should be able to pretty much go back to most medium tracks and fc a buttload of them (if you wanted to, i personally couldn't really be bothered to go back a difficulty, it feels too slow and boring if you are already on hard/expert)
keep it up tho bud, cuz it will be fun to play you when you nail expert.
edit: oh and you WILL be on expert soon if you just stick with it. because going from normal to hard mode is difficult only because you have to learn a new button, but going from hard mode to expert is really quite easy... it's just a bit faster and a few more notes the thing that will probably trip you up more is the weird chords that come up a lot. It took me quite a while to get my head around the Cherub Rock level those chords are quite challenging when you first come up against them, but you will be able to pretty much do it with your eyes shut after a lil bit of practice.