Simple answer Clarity.fm

It can happen if you are changing URL's , I would recommended if you are changing url's then make a list of all Url's of your website for that you could use scream frog and 301 redirect old url's to new.

The best answer i could suggest is Rel canonical.

I would recommended.
1.Content creation(should be solving problems)
2.Monitoring unlinked brand mentions.
3.Reverse engineering competitors backlinks.
4.Making use of social media by making relations with influencer.
5.Proper on-page
6Long tail keywords.

I would recommended:-
1.Make clear product hierarchy.
2.Proper product categorization.
3.Create separate sitemaps for products, categories and blog.
4.Use interlinking.
5.Use rel next and rel previous on product pages.
6.Use rel canonical on pages with session ids to control crawl budget.
7.Try to include more products on main categories instead of dividing them to multiple pages.
8.Use breadcrums.

You can Re-Submit sitemap through Webmaster or use Fetch as Google Bot option in GWT.