Kathy, a high fibre diet may increase the cramps if you have spastic colon. It is an excellent way of preventing cramps, but it’s not necessarily a good idea when you have cramps.
Anyway, that’s not your question. You should avoid any painkillers that contain codeine as they can make you constipated. You shouldn’t take any painkillers without having tried antispasmodics first. You can try something like Mypaid® and if that doesn’t work, something like Xefo®. The best would be to not take painkillers at all and to have the problem sorted out by a gastroenterologist. Good luck.