1996 Toyota Camry Lost forward gears

My transmission has been "slipping" for a month or so now. For years it "hesitated" into Overdrive. Two months ago I decided to change the fluid, filter, and gasket. The Toyota tranny dipstick says only "Dexron II" so it's what I put in. Couple weeks later, after trying to plow through a snowbank, it stopped shifting into overdrive. A computer indicated the "shifting celenoid B" was bad. Did not change the celenoid. Two weeks after that, it shifted again into overdrive. I drove it a long ways on a cross country trip, after which it began to have serious "slipping" problems in ALL gears except reverse. Shifted hard cold while hesitating bad into next gear and would only "work" if I "revved" the engine. At a stop it needed high engine RPMs to enagage the tranmission which still slipped bad. I was assuming this whole time it was the "shifting selenoid" as the computer told me a month ago. I just changed both shifting celenoids myself inside the pan after it refused to engage any forward gears following a high speed interstate drive, maybe I did not install them right? Or maybe the entire transmission is shot? I thank you for your recommendation.
Jared