Thank you so much for your replies!
I spoke to my boyfriend again about his trip, and I do feel much better. I know that he loves me, and his loving his other girlfriend or getting to share these new experiences with her isn't going to stop that. In his words, they are more likely to come back dead or broken up than monogamous.
@AnnabelMore: I don't have any ill feelings towards his other girlfriend, and the reason for my jealousy is the fact that she gets to spend so much time with him that I wish I could. But, yes, that's not her fault.. it's the distance. And we've been doing very well about communicating with each other regularly.
Also: I have come to realize that I am very monogamous, and it's not fair for me to lead a guy on by dating him (which I was). I accept the fact, and I know that I have enough on my plate to keep me distracted from missing him.
@Mya: Thanks for giving me a scoop of what's it like being on the other side. It's very easy to fall into the trap of thinking that since he has someone else with him he won't be missing my company as well. Reading what you wrote, and speaking to my boyfriend gave me some reassurance.
I will definitely check out your blog!
@Magdlyn: We're going to try and keep in touch as much as possible. I don't want him to text me because that can get pretty expensive with international rates. But, I will let him know that I want him to try hard to email me about once every two days.