Can u get an infection or std by using a shower hose for self pleasuring purposes?

NO: Not if you are using a clean hose

Possibly: This would be much more likely to happen with females, but f the water stream were irritating enough or strong enough to push bacteria back retrograde through the urethra, this could led to a UTI. You can't get an STD that way though - by definition, those diseases are "sexually transmitted", not shower hose transmitted.

No: Assuming you aren't putting in your vagina no. If your are placing water in your vagina that could cause an infection.

No treatment needed: not if only the water hits you. yes if you come in contact with a dirty hose

Very unlikely unless: It is extremely unlikely, unless due to scalding or direct trauma.

Yes and doubt it: Infection- clearly possible if hose not properly cleaned after each use for showering or anything else. Microbial entities will colonize that thing 9 times to Sunday just by virtue of the humidity. STD's? I doubt that unless a male got his infected urethral discharge on the hose which would suggest he were using similar self pleasuring technique which is doubtful unless he were masochistic.