first of all, it probably will make ou tired. Second of all, there are side effects, as with all SSRIs but lexapro is said to be one of the less invasive ones. TAKE IT WITH FOOD!!! If not, your stomach will be very unhappy with you. You may also suffer from insimnia, nausea, chills, increased anxiety etc. Not trying to alarm you, but make you aware that all of these are normal. You may also need to start off at 5mg and build up to 10. Many ppl on here, including myself, have had to do that.
As far as the happy pills go, I am not a fan of them, but I cant believe your PCP wouldn't give you any. SSRIs take at least 2 weeks to get into your system. He should have at least given you a script for like 1 to supplement you if need be. Here my dr's hand them over like candy and you can't get them. It just goes to show you how one dr opinion and treatment varies from one patient to another. No wonder we're all so screwed up.
Good luck with the lex-it really will help, just give it time