Should he get this worked up??

I'm goin on holiday for 3wks at the end of June with a gf. My partner of (currently) 10months does not like the idea as he does not like me going away for periods of time without him. I mentioned how long it was till I depart (5wks-excited!) but he just grunted n got really depressed n stayed that way for a while. I love travelling but I dnt like being made to feel guilty about it! Iv tried explaining how important travel is to me but I dnt think he quite gets it. He just doesn't like us spending time apart. How can I help him see things the way I see them and support my travel, cz there's guna b much more in the future...
Oh- he also thinks I should cut it short as I will b away for our 1yr. But as iv explained to him- I had organised alll this (including dates) b4 we started dating n I'm travelling with a friend so Its just not possible...