Hi
This could be serotonin syndrome if not, some other adverse drug reaction as all those symptoms started after adding paroxetine, so plz stop taking paroxetine (though you are taking small dose) wait for some time, if desvenlafaxine is not giving result you can slowly taper and stop over 3-4 days, then you can reinstate paroxetine.
Next Steps
plz visit a psychiatrist.
Health Tips
tab.cyproheptadine 4mg twice/day for 3-4 days & you can stop.