Bleeding three times a month?

So I'm pretty sure I've posted about this in here before but it just happened again so..

I called my doctor today and told them I'm tired of bleeding so often and don't understand why it's happening. They called back today and just prescribed me birth control. Which is exactly what happened last time and at my appointment I brought it up and they said the birth control should help and that's all. I'm annoyed because I don't just want birth control, I want to know why I can't be regular.. Am I wrong to be annoyed? Does anyone else experience this? Did your Doctor listen?

Edit: I took the birth control last time but my insurance wouldn't pay for three months at a time and it just didn't get renewed or something so I stopped taking it.