I went into the shower and used a detachable shower head to wash my body including my body parts, penis and anus included. I am slightly paranoid when it comes to hiv/std's infections. If someone had used the shower head immediately before for masturbating and some body fluids were left on the shower head would that pose a risk for me when I used it to spray myself with the water, an awful lot of water coming out from this shower head? Thanks for taking the time to alleviate my anxiety.
Thank you for your inquiry. From what we gather from the question, you were asking about acquiring HIV from a shower head. From the information given, this scenario is determined to be no risk (transmission of HIV is not possible in the given scenario).
The scenario mentioned above does not meet the three components of the transmission equation. It does not satisfy the equation because as stated by the CDC, "HIV does not survive long outside the human body (such as on surfaces), and it cannot reproduce outside a human host."  For a risk to exist, specific HIV+ fluids (e.g. semen, pre-cum, vaginal fluid, rectal fluid) must come into direct contact with the bloodstream of an HIV- person. 
Recommendation: No need for HIV test with the scenario provided, refer to a physician for other health related questions.
Regards, AIDS Vancouver Helpline/Online, Ashley