Your Google Form decides which column to store the data in - you do not control this.
And the design you're aiming for (different weeks data in different columns) is likely to cause long term problems. But there is a better approach:
In general, the first column in the sheet which it stores data in is labelled Timestamp, and contains the date/time when the data was entered.
Each column after that contains data in the order in which the question was added to the forum, ie:
- Column B gets the answer to the first question you added.
- Column C gets the answer to the second question you added, etc.
These relationships are maintained even if you re-order the questions on the form.
You can add helper-columns to the right of the ones filled in the by the form. So you could add "week submitted", and use this to calculate the value from the Timestamp column.
Then use a pivot table (or similar) to create a summary of the data, with the "week submitted" as the column value. This will give a view of the data like what you described originally, while still using the Forms data storage approach.