As a medical student, I wanted to read more about this so I searched in UpToDate (a database for some of the most up to date medical literature), and here are some select citations of what UpToDate (article:
http://www.uptodate.com/contents/hematospermia) said:
"INTRODUCTION — Hematospermia, the presence of grossly bloody or blood-tinged penile (seminal) ejaculate, is an uncommon condition. While it is usually alarming to patients, the cause is almost always benign. Only a few case series have been published, nearly all of which are from urology specialty practices.
Because of the paucity of research literature, there is little evidence on which clinicians can base their evaluation of patients with hematospermia. Searching for the rare causes that have been identified in case reports is not likely to be productive, and the relative frequencies of causes reported in case series from urology specialty practices may not apply to primary care practice. The most important lesson from the literature is that hematospermia is almost never a sign of cancer in younger patients."
Also:
"The major conclusions drawn from these and other studies are that hematospermia is almost always caused by a benign condition in younger men and, in many cases, no clear cause can be identified. In older men with hematospermia, genitourinary cancers should be considered in the differential diagnosis, but the rate of such cancers is low, even after long-term follow-up."
And, in the patient information section (this is what you will be given as a handout after you leave a doctor's visit):
"●In most cases, the evaluation will not identify a clear cause of hematospermia. Thus, there is no specific medical or surgical treatment for the majority of patients, and the condition will usually resolve spontaneously.
●When no serious abnormalities with hematospermia are found, the most important therapeutic intervention is reassurance."
It sounds like the OP had a very thorough work-up for a bunch of etiologies from an expert urologist. So, at this stage, if cancer/infection etc has been ruled out then I would encourage OP to relax, and go back to provider if symptoms worsen or exacerbate.