Anna, I am so very sorry about these circumstances. It must be a disappointment to be denied a raise as well as accept less than your peers get, even other than the loss of fun money, although that is where you're focusing your pain. I understand this as a coping mechanism, but I think you've also had great thoughts and advice on maybe diluting or even burying (again, depends on your will power and needs -- i find cold turkey easier than window shopping but not buying, say) the fashion focus a while.
It does NOT need to be drastic. As Claire said, taking your style in the high-low direction can be fun too.
Not much to add to what everyone's already said, but just had a thought: Could your craving for creativity be satisfied vicariously? Could you volunteer at a children's ward, seniors' home, DFS or similar, where you can help others play dress-up? Of course, without straining your own health further.
Alternatively, if you feel it is too hard to bury your favourite hobby, how about making it a focus from a different direction? Besides IK's and Rae's suggestions for DIY and your existing knitting hobby, could you perhaps take a course in fashion history or something to immerse yourself in fashion and keep 'busy' there without needing to shop? Go to museum shows and such. Treat yourself to a window into fashion rather than the front seat at the runway maybe? Make a project of street fashion photography perhaps...
Also, I think Angie's budgeting idea is the most practical to start with --- set aside a sum, and when it's gone, wait till next month. You can hone and tweak as you go along, but don't get trapped in 'fashion math' (borrowing against next month's, quarterly budgets etc) just yet. Keep it simple while you adjust to those first few smaller pay cheques.