Love isn't about ownership and control. It's about honesty, trust and respect for one another. You've been living together for 2 years and the relationship is going well, so I assume you're very committed to each other. You're no longer a couple of hormonal teenagers - you're two adults who need to deal with adult issues.
Jealousy and mistrust is *never* a good thing. Also, the concept of whether you 'allow' him to go is very dangerous territory. He's not your possession or your child. He's a grown man.
Don't react out of fear of the unknown. Have you sat down and explained your concerns? Don't be accusing, just share your thoughts and feelings and remind him that what you have together is so precious and isn't worth being lost over a holiday fling. He'll no doubt be adamant that he would never do such a thing, but should he find himself in a difficult situation, he'll remember your words which will reinforce his already deep commitment to you.
Don't let your mind make a mountain out of a mole hill. It will drive you crazy if you let it, so make sure that you're keeping yourself busy whilst he's away. Pour some of your excess energy into your hobbies, interests or even find new ones. Use the time constructively and then, when he gets back, you'll both have lots to tell each other plus the bonus of some wonderful 'back together' passion.