Blood in urine?

Went to L&D last night for monitoring and lab work due to suffering a horrible headache for days with no relief. Since having a history or preeclampsia before, they did some blood work and urine analysis to rule it out, which thankfully everything looks good in that department. But, the urine analysis showed that I have blood in my urine and we don't know why. No traces of a UTI or anything. I go on Monday to see my regular OB and have a recheck done on my urine to figure things out but now its got me a little worried. Any other mamas experience this??