My boyfriend just got back from Afghanistan and the drs put him on... xanax .5 mg 3 x's day / zoloft

... 100 mg once a day / darvacets n 100 i every 6 hrs and metformin 500mg once a day... is all this ok to take together? and he stopped taking all of it and is acting really off the wall now... bought a car that didn't work and now very abcessed about grtting it on the road and thinks of nothing or noone else..does this sound like side effects of stopping all this at once?