Do not use B. caapi in any form when on an SSRI. This combination can lead to serotonin syndrome, hypertensive crisis, and in some instances can even be fatal.
Sorry for the dramatics, but that combination is hugely contraindicated. Stick with DMT alone. If you want to explore harmalas and changa, do it when you are completely off any SSRI medication.
Because of competition for the receptor many people on SSRI's report mushrooms and DMT being less effective. Not everyone though. Always start low and work your way up to see how you personally respond to these substances.