"in the last weeks" or "over the last weeks"

English as a Second Language English Vocabulary, Grammar and Idioms
1

Future

I’m going to travel next week.
I’m going to travel for the next weeks/week.

Is there any variation depending if “week” is plural or singular ?

Past -> Until now

I’ve been working over the last week.
I’ve been working over the past week.
I’ve been working in the last weeks/week.

To mean “throughout”, the beginning of the action until now, which of those sentences above are right ? I also got a little confused about “last” and “past” concerning those situations. In addition to it, when the noun week is in plural or singular, is there any change in the structure ?

Thanks in advance.

2

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Is there any variation depending if “week” is plural or singular ?– In meaning? Only the obvious one of length of time.

To mean “throughout”, the beginning of the action until now, which of those sentences above are right?-- The first two suggest this more strongly.

In addition to it, when the noun week is in plural or singular, is there any change in the structure ?-- See above.
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