I've been on Yaz for only 1 month, and am trying it specifically to treat my severe PMS which it is highly prescribed for. As important as that is to me, I'm really frustrated for feeling like I've gained 4-5 lbs (and I'm a fairly small sized person, with plenty of breasts, frankly, so 4-5 lbs AND bigger boobs isn't easy to ignore). I've experienced no negatives aside from feeling heavier and tighter in my clothes, but I really hope it is something that will balance out after sticking with it longer. I too workout regularly, and eat a decent diet.
What I would suggest if you haven't tried, and you are doing everything else to maintain your comfortable weight, is a diuretic/ water pill. I've been using over the counter like Diurex, or AquaBan. There is no side effect, other than peeing alot, and you have to be drinking alot of water, which you said you do. I think most of the fat feeling I'm having is water retention, and that's what those are for. It's a cheap, safe thing to try. Hope it's helpful!