Hi Orejona
Im sorry she is having ongoing issues. What antibiotic has been helpful to overcome the infections? How long is she typically on it each time?
Have you had any xrays done? This could show if there are any stones or sediment build up at all.
No crystals in her urine sounds unusual to me. Rabbits should pass some sediment. Is her urine any particular colour or colourless?
Is she getting urine on her fur around her genitals at all?
Is she peeing outside of the litterbox more?
Does she seem conscious that she is uriniating or is she just leaving drips around or puddles while napping?
I do recall a member getting on top of chronic urinary infection by stopping the cycle where the rabbit seemed to be re-infecting themselves. While their rabbit was on an oral antibiotic, they also routinely wiped her butt area with pet safe wet wipes that contained an antimicrobial.
If a rabbit is getting soiled, a sanitary shave around the genitals can help stop the urine collecting in the fur, causing skin irritation and re-infection.