What Causes Bruises On The Mid Section Of The Body?

Hi, i'm a 49 yo female, I woke up yesterday with a series of 5 bruises approx 2" across running from mid stomach about an inch above the belly button wrapping around to the left. I just noticed today that i have a bruise forming on my left side under my bra line. I have not injured myself nor has anyone been using me as a punching bag.