It is not that your spinal fusion
got to do with pain, suceesful surgery will prevent all movement there and nerve impingement so cause for pain is not it.Your doctor should gradually shift you on alternative pain killers if at all needed.Heavy periods
has got something to do with hormonal imbalance probably, and a gynecological consult is necessary.If USG is not finding anything, simple anti-emetics before periods must be taken and may be prescribed by gynecs specialist after giving you internal check and hormonal profile.If you are having abdominal pain
, then maybe colonoscopy
may be necessary for bowel symptoms/findings that has made your doctor think on those lines.