You indicated that you have only been on 10 mg of Lexapro (Escitalopram) for about four weeks now. 10 mg is the lowest, therapeutic dose of Lexapro. So in reality, you should just look at the fact that you have been on Lexapro for a month, not three months. Anti-depressants take time to work, normally 3 to 12 weeks on a therapeutic dose. So you are in the very early stages of the medication's therapy. It's not uncommon at this point, to have good days and not so good days. I have been on Celexa, Lexapro's sister drug, for nine weeks, and I am still have some ups and downs. It takes time for these agents to work, so try to be patient.
Insights (Ian) pointed this out to me a month ago... "For some the antidepressants switches on almost instantly, for others it is a steady linear progression and for some the improvement comes in fits and starts, one step forward, two back for a week or so. IME, this often signals a slightly better long-term outcome than with the first two." So in his opinion, it's better to be seeing these these ups and downs.
As always, the very best to you, Lynn!... Chuck