Well, if you have all your ports forwarded, then the only possible reason is because the torrent you are downloading has no seeds. Seeds are basically your speed. The more you have = better download rate. As for your upload rate, I think it depends on what you set your upload rate to be. I dont know what client of BT you have but I have BitTornado and it allows you to set how many people can download from you. I'm not sure if Azereus (another client) or the official client can do that as well.