Birth Control

So I have really bad periods & they always come either too early or too late (usually too early) and it's EXTREMELY heavy the first 3-4 days and my cramps r bad throughout my entire period (even sometimes up to a week before it starts). Then the last few days r really light. So light that it's barely there & I don't understand my flow can't just stay more consistent. I have an apt coming up & im going to try to go on birth control but I'm not sure if it's actually going to help with this issue... any advice?