Long term pill user, sudden acne break out?

Hello! I've been taking Yasmin since Feb 2006. It's been working fine for me except giving me dry skin and low drive. I've always had very clear, good skin but recently I noticed that I got lots of bumps/whiteheads on my cheek. They're not red acne so it's not very noticeable. They just really bother me. I have not changed my diet or skin so I really don't know what's causing those white bumps. My question is: can you break out after being on the pills for about 4 years? Can you have hormone fluctuations while on the pill? Is it worth changing to another brand for these mysterious bumps?