What Causes Bruising On The Thighs?

Hi i am 23 years old and for about three months now i have been getting bruising on my thighs out of no where. I have not fallen or had any trauma to my thighs and they are starting to get bigger and worse. I plan on seeking medical attention but wanted to know what that could be a symptom of. I have not heard of hemophilia running in my family.