Its not a weak negoatiation position that the OP didnt do his original due-dilligence. If he is employed at will, he can resign immediately and that is his barg

Its not a weak negoatiation position that the OP didnt do his original due-dilligence. If he is employed at will, he can resign immediately and that is his bargaining power. Said that, no reason to believe the company is acting in bad faith, they were offered a bargain and took it. As it was posted, the best thing you can do to leverage and feel comfortable in your position is interview for another job, however, i would talk directly to your employers and talk about this directly. Its probably better for you to suck up a month or so with a bad salary than start looking for a job from scratch which might take you as much time. You can atone the initial mistake with one cheap month of salary, and negotiate the next one. If the company strongs their position, you can always look for an alternative.