Im currently on 10mg lexapro day 16. I was wondering, since before I was on it and started at 20mg
You were started on the maximum 20mg? Do you know why? The usual Lexapro starting dose is 10mg (though 5mg is often better). This is also the most common maintenance dose.
and had no side effects and it worked quickly, this time around i had more side effects and it seems like its taking longer to work what is the reason for this?
A very good question with few answers so far. But it does seem to be the case that antidepressants will often produce more severe and/or different side-effects the second time, that a higher dose may be required to get the same result as the first time, and there is an increased likelihood of the med not working at all. According to one study
the odds of antidepressants working drops by about 20% each time. This applies to all antidepressants, not just the one/s taken previously.