I get really bad cramps too...

When the above things you mentionned didn't work for me,

1) Chocolate. Dark chocolate mostly. Don't ask why, but it made the cramps go away temporarily

2) Bath. You said you tried a cold shower, how about a warm bath? Aromatherapy and darkness/candles also seem to make it easier.

None of these actually get rid of the cramps, but they can make them easier to deal with.

Hope you get over the evil cramps soon!!