What Could Bruises On Leg And Thigh Suggest?

hello, for the past 2 months I have been getting unexplainable bruising on my legs. At first I thought i bumped it and just didn't remember. February it got really bad. I had a huge bruise on the outside of my thighs both of them. Then about 6 or 7 more just randomly on my leg. And one of the big ones still havent went away, and it has been about a month ago that I noticed it. Should I start getting worried?