Lexapro side effects

I've been taking Lexapro for 2 1/2 years for anxiety and depression. In the begining it worked fabulously. My bouts of sudden rage and then horrible sadness were gone. I felt like I could finally be a normal person. I was a better wife, a better mother, and I could function at my stressful job. But this past year I've been having difficulty with concentration and memory loss. It just seems to be getting worse.
It's difficult to function at work. I made an appt. to see the Dr. and forgot to go to the appt. Sometimes I find it difficult just to complete a sentence or answer a simple question. I cannot continue like this. I feel like I'm slowly losing my mind. I have a masters degree,but at this point you'd never know it. I've stopped taking the meds. but the withdrawls are terrible. I have dizziness, vertigo, headaches, lethargy,brain zaps,ringing in my ears and I then feel very disoriented, night sweats, .....shall I go on? I'm taking 20mg. Should I stop the meds? If I take a lower dose will it help with my inability concentrate and remember things? I don't know what to do. I don't want to go back to the old depressed me, but I can't function in my current state. Help