I've been on yaz (drospirenone and ethinyl estradiol) for 4months.now i spot 2 small ecchymosis on leg that i don't know of the cause. there's no pain or swelling.could this be a problem?

Probably not: There is a difference between ecchymosis and a deep venous thrombosis. Without swelling or tenderness it is unlikely to be anything worrisome. Yaz (drospirenone and ethinyl estradiol) does have a slightly higher risk for causing DVT than non-drospirinone containing ocps, so we always worry about them. If you have concerns have your doctor examine the leg and determine if any more studies are needed.