Clavamox is not the best antibiotic for UTI's. If you notice your kitty is still having issues after it finishes the first round, ask your doctor about switiching it onto Baytril instead.
You need to get your kitty some Nutro Gourmet Selections- Roasted Chicken (orange bag- you can get it at Petsmart, petco, and online). It is especially formulated for kitties prone to UTI problems- it is VERY good at helping with those issues! (it does have some grains/etc in it- but they are benificial from what i understand in helping kitties prone to UTI issues.)
Also- your kitty may start to go potty outside of the litter pan because it might associate the litter pan with pain (as a result of the UTI). If this should happen- get your kitty a brand new litter pan (old ones, even when clean may still have superficial scratches which will hold the odor of their urine and remind them of their UTI issues.) and add some Cat Attract litter to the new litter pan- this stuff works VERY well. It takes a little consistancy and patience- but it does work! It is a bit pricy- about $12-15 a bag- but you should only need one bag to get kitty back to using its litter pan if it does have issues. (pm me if you want to know more and i'll try and help!)
-EDIT- Clavamox takes about 7-10 days to really get into their systems and can take up to 2-3 rounds to knock out a UTI issue. Baytril or Doxycycline work MUCH more quickly and tend to have the kitty feeling better much sooner! I would suggest asking your vet about switching meds if you don't notice an improvement soon. (also- do NOT let them give you Amoxi or Amixi Drops- it won't do a thing
Be sure that if you do provide your pet with soft food right now that you avoid all seafood flavors- they will do more harm than good if your kitty has a UTI.
Stick to poultry flavors.