Muscle cramps

hello, I had bc in 2011 with another primary tumor in the right lung both surgically removed chemo and rads for the bc which was hormone receptive so had a few years on arimidex. In Jan this year went for check up complaining of lower back pain and yep we all guessed it secondaries in the bones several to be exact the most severe being in the lower sacrum near the nerve bundle so had some radiation followed by chemo taxatol herceptin and perjeta. Im on herceptin and perjeta every three weeks now as the fiend has changed its spots and has now become Her 2 + , I think I'm coping OK but I have been having the worst cramping and muscle spasms these occur at any time and in any muscle from head to toe I cannot exercise because stretching or contracting the muscle will cause it to cramp. I am taking all the vitamins and supplements recommended but to no avail. Resorted to seeing a neurologist he suggested Lyrica, but its not helping. What to do I'm at a loss,heart function took a dive last month so had to skip a round lucky it bounced back by a reasonable % so I was able to have my next round, you know if you go with out perjeta for any longer than six weeks the government will not renew the script so you won't get any more and its too expensive to buy it yourself now thats a (#**!!) bit of bad luck. Ah well thats enough complaining I'm off for a walk. Cheers Jenny