月经拖到十天左右正常吗？白带成黑色的，是有病吗？

健康咨询描述： 1.月经拖到十天左右正常吗？2.白带成黑色的，意味什么？
我今年37岁，我的月经常常到第四天就很少，五六天干净，到第十天左右又会出现一些较淡的血水或黑水，这样正常吗？
这个月是四日来的月经，干净几天后，前几天出现暗红的东西，到这两天内裤又沾上黑色的东西，今天发现黑色的白带（无味），这是以前从没有过的。一月份单位体检时做过涂片化验没有发现  不正  常，我现在也没有觉得有什么不适，这种象是什么原因造成的？                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

患者性别:


本次发病及持续的时间:
目前一般情况:
以往的诊断和治疗经过及效果:
病史: