How To Treat Bruise On Buttocks And Lower Back?

i HAVE BRUISING ON MY BUTT AND LOWER BACK.. i HAVE NOT BEEN HIT OR HAD ANY TRAUMA TO THOSE AREAS.. i RECENTLY WENT A WHOLE WEEK WHERE I FELT FINE BUT COULDN'T EAT ANYTHING, I SLOWLY GOT MY APPETITE BACK BUT THE BRUISES SEEM TO BE GETTING BIGGER. may NOT BE RELATED BUT JUST ALL HAPPENING TOGETHER