Side effects with SSRI's can take a lot longer than one week to subside. Sorry, but it's the truth. You have to bear with them, unless, like me they give you migraines and constant vomitting within hours of taking them, which is an allergic reaction caused by the serotonin receptors which line the stomach. If your side effects are severe, you are not required to grit your teeth through them, because the likelihood is that they will not go away. You must then consult your doctor and change prescriptions for a different drug.
You cannot know if an SSRI will work for you unless you give it the full 4-6 weeks trial. It is doubtful that you will feel much better before then, and even then, SSRI's are not magic cures. They will not have you turning cartwheels, you will still have to deal with the issues in your life which have triggered the depression symptoms. Antidepressants have a high failure rate. They rarely cure, unless your depression is 100% biological, and most are not. What they do is cushion you so that you can physically and emotionally work on improving your life circumstances.
The feeling funny in the head is one of the most common side effects, and it does wear off. It makes you feel slightly disconnected from the outside world, fuzzy-thinking, your brain feels cloudy, you may feel dizzy. These feelings do pass.
However, I am sorry to tell you that the sexual side effects do not ever go away with SSRI's. This is the number 1 side effect which makes people give up on anti-depressant drugs. There are several classes of antidepressant medications, and the SSRIs, of which Lexapro and Zoloft are both examples, are known for the high incidence of sexual side effects that they cause. The SNRIs cause this slightly less, so you may want to investigate them. Many doctors prescribe Wellbutrin (bupropion),an SNRI, in addition or instead of SSRIs to help counteract the sexual side effects. (The difference between SSRIs and SNRIs is that SSRIs target only the serotonin receptors in the brain, whereas SNRIs target serotonin and norepinephrine receptors also).
I tried Wellbutrin (SNRI) and Celexa (SSRI), which were the only antidepressant drugs my body would tolerate, for 2 years. I did not experience any relief at all, even after increasing dosages, but plenty of sexual numbing. At the end of the two years, I was so pissed off that not only did I have to be depressed, but I could not even enjoy or feel my own body, that I pulled myself off the drugs. I have never regretted my decision.
I still suffer depressive episodes and do not think that will ever change. But, what is required to manage them is acceptance of myself, acceptance of the fact that this is how I am, I will suffer these episodes and when I do, I need to not ask too much of myself. It is OK to feel, even if those feelings are deemed negative ones by culture at large. Also, what is required are lifestyle changes to manage the triggers of depression.
Depression is your mind's way and body's way of telling you that your way of life has become untenable and you need to make changes to make your living and being healthier for you. I wish you luck, and I also advise you to read about antidepressant medications and depression as much as you can. Start with David Burns' "Feeling Good, the New Mood Therapy."
Clare