I know that later can be replaced by after s + v like the following.
I wake up at 10 but I get up about an hour after I wake up.
I wake up at 10 but I get up about an hour later.
Then, how about this?
Since 3 weeks ago, I have been dating her.
Since 3 weeks before now, I have been dating her.
I just want to know more expression that is the same meaning as "ago", so that I can use more sentences.
Or better,
I met a girl 3 weeks ago.
I met a girl 3 weeks before now.
Are these possible?