How much soy is too much? What problem can it cause? I usually have 1 glass of soy milk, 1 bag (1 pound) of edamame, & 1 box of tofu. Is it too much?

Ask Grandmom. What does your grandmom eat? You will most likely do well with the foods that your ancestors eat [asians may not handle dairy and wheat so well. Anglos may not handle soy so well]. Most problems: powders & pills, not food. Your goal: keep your isoflavones less than 100 millgrams a day. [see comment for more info].
Soy may not be good. For all people. Eating large amounts of soy’s estrogen-mimicking compounds, isoflavones,  might reduce fertility in women, trigger early puberty and disrupt development of fetuses and children. I can't give you any specific amount that would be too much, but I do recommend limiting the amount of soy consumption in children and women trying to get pregnant.
Balance is the key. Balance is the key in life. A balanced diet means eating a serving of many varieties of foods. A person drinking 8 oz of soy milk each day sounds fine, but eating 1 pound of soybeans a day means 30 pounds a month . . . That sounds a bit much. Also, eating 1 box (4 big squares) of tofu a day means 7 boxes of tofu a week . . . Sounds like enough to make meals a bit boring. Again, variety is the key.