Does finding blood in my urine mean that I have bladder cancer?

Possibly. Blood in the urine (whether microscopic or gross) must be evaluated by a urologist. The degree of hematuria does not necessarily correlate with the size of the problem, so the evaluation would include laboratory testing, imaging of the urianry tract, and cystoscopy - a procedure to look inside the urethar and bladder with a telescope. Possible causes include infection, stones, and malignancy.
Possibly. Blood in the urine (hematuria) can be microscopic (found only with testing) or "gross" (seen with the naked eye). Most causes of hematuria are benign (infection, inflammation, stones, hormonal, kidney problems), but even microscopic hematuia in a person with no symptoms can be an early sign of bladder or kidney cancer. Depending on the situation, testing is often recommended.