I too was on Lexapro but switched to generic celexa (pretty much in the same family of meds but generic is much cheaper for me). I had to try several combinations of meds and these two seem to work for me.
As far as sleep, I take xanax at night to sleep. It is a very low dose but it helps to me sleep thru the night. I also take my celexa at night time as well. There are a lot of sleep aids on the market (ambien ...). But, many are addictive so you have to be careful. I sleep with a hall light on and a fan. The rhythm of the fan helps me to sleep. Another thing I do (this may sound a little strange being that I am 45!) but I always loved gymnastics as a kid, always wanted to be a gymnist (even though I have 2 left feet). At night, when my mind starts to wonder and my thoughts race, I imiagine in my mind I am a gymnist - a child on the gym floor tumbling to the music, listening to the crowd..... Again, I know that sound odd, but it helps me to focus on something I enjoy - something that made / makes me happy. It kind of forces the "bad" thoughts away. Helps me to re-focus my mind.
I know how you feel, like falling in a ditch. I felt like I was drowning. But I can tell you it will get better in time. Just posting on this site is a very brave step. It really does help to (at least me) to talk to others who know how you feel. I have good and bad days but the good days now far out number the bad.
It takes time. It takes time to heal.
I am proud of you for posting and getting help, this is a big step and one for you to be proud of.