Bad breast pain and needing advice

Hey everyone, I'm a ftm who just had a baby three days ago. She had a hard time latching onto my left breast at first and it's larger than my right so now it's like I have an oversupply in that breast compared to my right. I really could use some advice because this pressure is radiating down my arm and hurts bad.

I used my haaka on it earlier tonight (never pumped before that) just to get some relief while she fed on my right side and got an ounce out of it while my hubby tried to massage some of the milk out. That hurt like a mofo, like electricity running up and down my breast and into my shoulder/arm pit area. My question is how do I even out my supply in both breasts without causing myself to dry up? Also, all of the milk in my left breast is on one side, causing a lot of pain. How can i express this without causing my breast to make more milk in the long run? Help!