Hello I am pregnant 10 weeks now , and have...

what might be the cause ?
light bleeding during the pregnancy is very common throughout the whole pregnancy stages and there is nothing to be worried about and the patient usually decribe the bleeding as spotting but in some other cases in case of severe or considrable amount of bleeding its called a threatned abortion and in such cases the doctor will advice you to keep calm and not to do anything physical 
what are the causes of the vaginal bleeding during pregnancy ?

• although you dont have a period during pregnancy but at the time of the expected period you might have such vaginal spotting 
• inflammation of the cevix 
• missed abortion 
• cervical polyp 
• if you are pregnant with twins you will have a higher chances of 1st trimester vaginal bleeding 
• ectopic pregnancy 
• molar pregnanacy 

what are the diagnostic tests ?
the doctor will exam the patient using and ultrasound to check for any abnormailty and might do a pregnancy test via blood to check if abortion is suspected 
what is the advice ?
if you feel no pain and the bleeding is light so just carry on and no need to visit the doctor but in case you feel pain or heavy bleeding so visiting an obs and gyn is a must