When background is being checked, case status not changes into application pending because background is linked with decision, not with the application. If the application is pending, 90% cases receive negative decision, only 10% get approval, in that case when status again changes to decision is pending.Most likely they are doing the background check but it has not good or bad sign at all a lot got approved after application is pending and a lot got denial too so it means nothing but your case is actively reviewed