Most people do notice that the antidepressants begin to work immediately to improve their mood etc.
And some people do feel side effects of the antidepressants immediately and sometimes it takes a few days to a week to notice any side effects of the antidepressants.
Usually antidepressants make some people feel a bit worse during the first week or two before the antidepressants make the person feel better.
So if you notice you're feeling worse after taking the antidepressant medicine it's normal for a few weeks or so but then you should begin to feel much better afterwards.
If you continue to feel worse though with the antidepressants then you should speak to your doctor about it.