It's really important that you are asking these questions, because your conclusions are limiting your perceptions.

There are two aspects to a drug's toxic effects: the chemical structure, and the dose. The result that you've experienced so far isn't just due to the drug's chemical structure, it's also a result of how much you took. It may well be that you took the recommended dose, and nothing more, but your individual body chemistry sees that as an overdose. You may well have a positive response on a very low dose of SSRIs. There is a pediatric liquid formula for Prozac, as an example, which allows you to take tiny but precise doses of fluoxetine (dose is exactly proportional to liquid volume). That's just one angle on what is possible; those very same drugs, taken differently, might work for you.

You don't mention what drugs you've taken, but there are the MAOIs (monoamine oxidase inhibitors), there is Wellbutrin (works on dopamine exclusively), there is a serotonin reuptake enhancer (tianeptine/Stablon), there is the possibility you'll respond to tryptophan (the amino acid precursor to serotonin), or light therapy (this is the time for the onset of seasonal depression), or ? I'm sure a psychiatrist can handle the challenge.

Please make the appointment, and be sure to obtain all the records of those prior incidents, if you can. At least, get a letter from your doctor detailing the adverse reactions, the drugs involved, etc.

Good luck,
Lar