If I had the opportunity to speak with you in person I’d want to know how long the entire relationship has lasted. I’d also want to know how he “pursued” you to try to get you to forgive him for kissing another girl. Also, what now makes the relationship “official?” Does “official” mean he is willing to see you exclusively? Does it mean that you are a couple? These and other questions would be helpful to have answers to.
Early in the relationship the two of you were having sex but apparently there was a misunderstanding on your part. From your perspective you thought the two of you had more than a sexual relationship. The proof is that you were upset and bothered by the fact that he did not call you on a regular basis. You apparently thought it was more than “sex only.” Your expectations were unrealistic. From his perspective he might have thought since you and he were only engaged in a “sex-only” relationship that it was okay to kiss another girl. Technically in this situation, as you noted, he was not cheating because the two of you were not “official.” Having sex does not equate to a relationship.
I should also note that this situation is unfortunately common among women. They have sex with a man after a relatively short period of time and then are upset when he doesn’t call regularly or does not take their “relationship” more seriously. The truth is that in many cases if sex takes place it was only sex and no real relationship has begun. Some women do not realize this and then are disappointed when the “relationship” does not develop in the manner they think it should. I mention this because it is important to be realistic. Sometimes sex is just sex. If you want more than a “sex-only” connection with someone then it’s best not to begin a potential relationship with sex. It’s better to establish a relationship first and then consider sex later. Doing it this way may weed out the people who only want to use you for sex and have no interest in establishing a relationship with you.
I cannot predict whether your boyfriend will cheat while he is away. At the time that he kissed another girl you and he were not “official.” As I mentioned above, when you and he first met there was a misunderstanding on your part about the status of the relationship. Now that your relationship status is clear (i.e. you and he are “official”) you might have to be less concerned about him cheating. Remember technically when he kissed another girl it was not cheating since you and he were not yet an established couple.
Is your anxiety justified? That is a difficult question to answer. I’d need to know more detailed information about the relationship to determine whether you should be concerned about his behavior on the trip. I’d also need to know other information such as how the long two of you have been “officially” a couple to gauge his potential for cheating. Generally speaking, not many people would be comfortable with the idea of their significant other on a trip with another person. In this situation it may be reasonable and justified to be slightly anxious about their trip together.
As for how you should behave in this situation, generally speaking you should act rationally. You might want to find out whether you could go on the trip too. Does he have to go? You mentioned that another person was attending the trip and I am wondering if that is the only other person going. If you can’t go then that is fine too. Ask him to call you daily. On the phone act as you normally would. Give him the “benefit of the doubt” unless you have reason to suspect otherwise. That may be all that you can do. Thanks for your question.