it sounds like increased anxiety due to the lexapro. anxiety can those are anxiety symptoms. they are also side effects. during acute phases i've felt like that. that's not to say the increased anxiety isn't caused by the drug. it probably is.
i really think your gp messed up by exposing you to too high of a dose at first. also, lexapro tends to be sedating to most people at 10mg. it can be mania producing at 20.
one thing you might want to try is breaking up the dosage. break a pill so that your taking say 15mg instead. this might help out a great deal. also, if your taking the entire dose all at once you might try breaking it up into two doses or even four.