I just took a urine test at my gyno and my dr said that there was blood in my urine. obviously not enough to be seen by me. what does this mean?

Microhematuria : = blood + in urine + seen under a microscope. Can be due to infection, irritation to the urinary tract from a stone or infection even in the past. Sometimes a heavy workout can cause muscle breakdown, or myoglobin, which can test positive for blood on testing strips, while there no blood under the microscope. If your urine is culture-negative for infection, repeat the test in a few weeks.

Neoplasia/Nephritic: It can also be associated with tumors (both malignant and benign) of the kidney, uretor, bladder or urethra. Additionally if it is accompanied by protein it may be from a nephritic syndrome -- a by product of a disease of the the glomerulus. This will usually have a corespondent drop in kidney function. Hematuria may be spurious as it sometimes resolves on repeating the ua, which i recommend.