I have been self cath-ing for over two years and haven't had any infections so far. (Anxiously looking for a piece of wood to knock on)
My urologist also told me I could use my catheters more than once as long as I cleaned them well. I get four a month on my prescription and am just careful to wash them with anti-bacterial soap, always at home and soap anywhere else. I am very careful to not use a cath, if it touches any surface, without cleaning it. I always carry two with me when I go anywhere.
Are you using surgi-lube sterile lubricant with the cath?
I may just be less susceptible to UTI as I've only experienced them a few times in my life.
I have to say the self cathing gave me back my life. Prior to this I was famous for knowing where any bathrooms were whenever I went out with my friends. It is great to see a whole movie also.
Wish I had more suggestions for you. Good luck with this. Take care