Yep, again the DH might happen in your 5 working days and lately that has been the case but if you out of base from a place with not so good connections then you might only be able to DH back on you day 1 off. You won't lose your days off for a flying duty including the ones out of the active week. If they roster you for that, just ask them politely to remove it and they will, don't have any choice really. The only time you only have 3 days off and work 6 days is during your simulator week, twice a year.