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Thanks for a very new question! I never been in to this kind of problem but i guess if you are facing such kind of problem you should consider using this plugin (http://wordpress.org/extend/plugins/seo-blogger-to-wordpress-301-redirector/) as this plugin will 301 redirect all incoming traffic from your Blogger account to your newly setup WordPress account. I know using plugins is not an easy job all the time but i guess you can check with one and then move to others if it worked well for you~

Yes, you are right.  Thank you Ryan!

Thanks a lot for all your responses, they have been of great value. I'm getting the info about the keyword behaviour from Seomozpro campaign. The same keyword has gone up 10 positions this week without doing anything, so it's quite strange this going-down-going-up without any aparent reason... Maybe it's going up to its previous position? Let's see.. Thanks a lot for all your help!