Are you able to go to your vet and get food called s/d? Chances are the crystals are struvite, and s/d stands for struvite diet. It would help to dissolve the crystals. You can't know for sure if they are struvite crystals without a urinalysis but it might help. I would at least call the vet and ask if there can be a payment plan put in place. Where I work, a straining/blocked cat is considered an emergency.