I know how you're feeling. Been there done that myself...a lot.

This early in the relationship, I think you are asking too much. Also, I believe you may be misinterpreting his "disinterest". He probably has no clue how much you want to go on the trip with him because he may not understand why you would want to. A lot of men don't like to mix their work and personal lives. They might have very stressful, demanding jobs and they don't want their loved ones to be exposed to it.

I know it's hard, but try to find something else to do that weekend to keep yourself busy. Make it something really fun and enjoyable for you, so you're not tortured the whole time missing him. Besides, it will give you something interesting to tell him about when he comes back. You want him to see you can be confident and independent even without him around. Find something to do...besides him...and it will keep him interested and motivate him to give you more attention.