honestly i'm not entirely sure. it might be the location on your wrists that makes it hard. when i sh'd i noticed the higher i cut on my wrists/arms. the less blood there usually was. that's because theres not as much skin or anything, the bone is basically right there.
it might also be how your cutting. you mentioned that you press pretty hard. i've done that and noticed that it's harder to get it far, but also less blood. i recommend quick light/medium strenth slices more-so. you'd be supprised how much worse it can get with that, so make sure not to go too hard the first time you do that, and slowly increase pressure as you wish moving foward.
be safe, be careful, use good aftercare, goodluck <3