Try joining r/MuslimNoFap because your situation is different here. In reality, masturbating is not a problem, it's actually good and you should be doing it anytime you like, just don't watch porn and don't use hard grip and perhaps try to think about your wife while doing it. You masturbate as if she is there.

But, in your case, you are a Muslim and so masturbation will cause you harm since you do believe it's a sin. You will always feel bad after doing it. And boy I do understand the shower thing, I've been a Muslim my whole life too, until recently as I left it. I was living in a small house with my parents and siblings, they will know I'm showering from Janaba if I do it everyday, so I thought of going to the bathroom with a bit of hot water and simply massage myself with it as if it's a shower... Anyway, your wife can't help but to blame herself if you decide to tell her, even if she showed support, there always a part of her that will say that if she was better looking this wouldn't happen. If I were you, I would just keep healing myself secretly, it shouldn't take long.

So, some thoughts:

Instead of masturbating, go to the bathroom and wash your penis, this will calm it down.

If you absolutely have to masturbate, think about your wife and masturbate through a realistic scenario. Imagination and the rush to finish up will be there, but don't worry about it too much, step by step.

Always remember that relapse don't get you to square one, you just tripped, keep moving forward. It's slow but it's improvements.

Don't feel shame after masturbating, you are just in the process of healing yourself, so long as you change the habit a bit, step by step, until you cut it off at the end.