oh we have ALL been there- i'm leaving Layla for a while this afternoon and feel horrible about it. But he feeds off of your energy- if you make a big deal about leaving and coming home- he will start to get anxious about it. When you come home be very calm say hi to him and go about your business- once he has settled down give him a special treat. Also try and have a routine for him. When i leave Layla i put a special blanket on the stairs (Where she hangs out when i'm gone) i tell her to "come give mommy a kiss" and then i say "Layla i will be RIGHT back" so when i do those three things she knwos i'm leaving but like usual, i'll be coming back. Try starting a routine tomorrow.. and when you leave.. make it no big deal. Maybe part of your routine will be giving him a special treat or toy he only gets when you go. At first he will have a bit of anxiety and that is normal but if you are calm and he sees taht you go and come back and it's no biggie- soon he won't even care that you leave (layla doesn't care anymore) Also when you get home make sure he gets a nice long walk
I hear dogs can't decipher time taht is longer than 20 min... but who knows!