Well...You have three different types of meds your considering. One is an ssri (pristiq). One is a mood stabilizer (Lithium), and risperidone is an A- typical anitpsychotic or neuroleptic.

All three from what i know are used for depression, bipolar, schizophrenia and ASD.
You could start with a new ssri and see how that works, If it doesn't work then move on to one of the other meds., but i would ask your DR and see what they recommend though.

Good luck