Skates issue?

I was fitted for new skates in January, and have broken them in by now (but definitely not worn down). They tried me in the half size smaller, just to ensure the boot wasn’t too large, and I couldn’t get my foot into the half-size smaller (so the boot being too large really shouldn’t be an issue). I put new laces on the skates a couple weeks ago, so I know the laces aren’t an issue, either.Right now, I have to re-tighten my skates every 20 minutes because they get so loose that I feel very unstable when landing jumps. Also, no matter how tight (unless too tight where I can’t bend my knees properly), my heels move very slightly (and then more as the boots get looser), which causes awful blisters after skating for an hour. I don’t know how to fix this issue. I already have superfeet insoles in my skates..I don’t know if there is another insole that could fix the problem..but I’m just out of ideas.