I noticed my breast is bigger, painful and swelling on one side. What should I do? I tried expressing the milk but there seems to be no milk already but i still feel very painful. The bigger breast has more milk supply compared to the other one.

Sounds like engorgement. You can try Sunflower Lecithin, available from iherb.com.. pump on a schedule. Like 3hourly and really stick to it. Message and fully empty each breasts and check for hard milk lumps. Ice pack doesn't reduce supply, it only temporary numbs the pain. Wear loose fitting nursing bra or none. If all else fails see a nursing consultant. Good luck.