Normally, 17% would be considered quite high (in fact, I'd say anything over 10% is at risk of being penalised/not accepted) - but I think Turnitin similarity checks are usually conducted without references included. The reason being that the references will obviously get picked up by the check (after all, the reference will appear in the original paper and any paper that cites it), but this is obviously not a case of plagiarism, as you are doing the right thing by citing your sources!
So I would first double-check what is required. It may be the case that your Turnitin similarity report isn't meant to include your references. If so, maybe submit your document without references for a new Turnitin check, and see what similarity percentage you get. If the references are meant to be included, perhaps consult your tutor/lecturer and see what they say.