No need for that, you’ll be ok for a few more days.
Answer to your first question is yes and no, depending of which two SSRI’s you are talking as many SSRI’s also have other significant action. So you can talk about certain chem like in your case antihistamine with some SSRI effects (idk anything about chem you named honestly) as tramadol is opiate with some SNRI effects and substituting those two for “real” SSRI or SNRI wouldn’t really work, while mix and matching “real” SSRI’s is quite usual practice in medicine. So if something doesn’t work for a few weeks or months you get new SSRI and if main action is indeed because that medicine is SSRI, in theory new medicine should “kick in” faster but it often isn’t so.
Hope I make sense, all in all, you wont have to wait weeks or months for your medicine to start working again for depression. What are you prescribed? Maybe your SSRI produces most of wanted effects in your case via some other mechanisms so it’s worth looking into that but it’s also possible you feel mild WD. Well in fact, it’s too many variables are unknown so I guess no one answered so far cuz of that..