By the way I am in philly and this plant is kept in door now.

On my jasmine this seems to happen quite naturally, and it also loses leaves in the way you describe. But this happens on the lower branches that are out of the sun.

So my guess is that your plant is not getting enough sun.

Sorry I can't be more help.

Here is a link that might be useful: Jasmine indoors

I - 2nd Julian's advise about the sun.
Down here in Florida, we grow these in the full sun.
They bloom all summer.
They do loose about 1/2 their leaves in the wintertime,
mainly the older, bottom leaves.
That's normal.
Did you stop feeding it?
It still should be given a small amount
of a 3 month fertilizer along with
as much natural sun/ light as you can................cheryl

Thank you all.
I did put it back on a south window. But one day later,it lost all its leaves.
Is there still any hope? :(