HI susan,
when my b/f and i have anal intercourse my b/f uses saliva as lube and it works very well but it tends to slide down to my vagina area. I was wondering if it possible for the saliva that slides down to cause a UTI. I almost always get them after anal intercourse. (he doesn't put his penis in my vagina after anal, so that can't be it) Thanks for your shared knowledge.

Yes, the saliva could be giving you an uti, since it is also very likly also picking up fecal matter too. He could also be passing it onto you with his fingers or his mouth.