30 grams of fiber should be enough, but try adding a couple of dry apricots, maybe a spoonful of wheat bran. You don't mention how much water you drink but 30 g. of fiber REQUIRES a lot of water. So even if you think you're 'drinking plenty' try adding more water (esp. hot water w/lemon, or hot tea, coffee) and add a spoonful or two of olive oil to something, daily.
I don't personally like to overload on Magnesium (I try to keep the cal/mag thing in balance) but if you don't like senna you might try megadoses ofvitamin C. 8 or 10 grams, can't hurt ya and at a high enough dosage Vitamin C will unclog Rome.

Finally...most Asian grocers stock a 'slim tea' or 'dieters tea', I've seen several brands. The tea includes senna, and works like a charm. Not as fast as the pills but not as rough on you, either.