My Wife Is Taking Shelcal 500mg Tablet For Almost 3

my wife is taking Shelcal 500mg tablet for almost 3 months now and we are suspecting it to be the reason for her now frequent headaches and nausea condition. She is fine if she doesnt take Shelcal for a week or so to observe. What do you suggest here? Replace Shelcal 500 with something else?

Thanks in advance.