started 3 days ago ,,, a small bruise the size of a golf ball appeared on the bottom left side of my stomach no pain and no apparent reason for a bruise to appear ,,it kept growing and getting more red and purple ,it is now the size of a tennis ball and even more purple the tissu on my stomach is soft i have stretch marks from having 3 kids and i do bruise often but never there and never that big of a bruise ,, i'd like to know what could of caused this and if i need medical attention thanks