Have you been depressed for a while now? If so, I doubt your problem is serotonin syndrome as it's very rare. Most people who are depressed are so low in serotonin that they'd have to take their entire month's supply of meds to trigger serotonin syndrome

Your muscle twitches sound like they could be a symptom of magnesium deficiency. Your med could have triggered it as psych meds block the body's ability to utilize magnesium so if you're already deficient [and most people are because of eating white flour and sugar, drinking carbonated beverages and the like], the meds made it worse. Add a highly absorbable magnesium to your supplements and see if it helps. You want to go with magnesium chloride, citrate, malate or other chelated form, and liquid or powder you mix in a drink is more absorbable. DON'T buy the cheap magnesium oxide that is sold as 'magnesium' as all it's going to do is giving you raging diarrhea as it's barely absorbed. You need to be sure and take calcium and vitamins D3 and K with the magnesium as the 4 work together.