Thank you, I’m sorry to hear that you are having so much trouble staying clean. It sounds like you have a lot of sites on a shared hosting server that is not secure enough to keep the hackers out.
The problem with conventional shared hosting is that if any of those sites has a back-door or a vulnerability on it that let hacker write files to your server then they will be able to reinfect all your sites on that server as often as they want to. It is extremely hard to track down exactly how they are getting in and plug up every security hole and back-door they open, especially if you have a lot of sites on there. Furthermore, it is possible that they are getting in through a site on someone else’s account that is not even within your power to fix.
I do offer Super Secure Hosting and I’m sure that would take care of this cross-contamination issue for you. If you would be open to moving your sites to my servers just let me know how many sites you are interested in hosting with me and I’ll let you know what it would entail.