<human>: ......you were in my (F/28) situation?

Your boyfriend (M/29) of about 8 months tells you casually that he's going to see a friend (F/about our age) of his in a town about 4 hours away next weekend.  This girl happens to be someone that he met a while ago online. They dated, hooked up an undisclosed but not large number of times,  and have been good friends ever since. She helped him with his phd, he helped her through a friend drama situation.  

Apparently, this trip had actually been planned and booked at least one week before he casually let me in on these plans, and it turns out it was going to be just the two of them. They will even spend a night with some of her relatives, though I guess that was mostly out of geographical convenience. He acknowledged that I am feeling like he's testing my trust in him. He went anyway. 

I really want to trust him and I want him to feel trusted. But. I have been uncomfortable about this all weekend and he gets back tonight.  I have not had a good track record at being tactful lately and I really want to say the right thing, but still let him know how I feel. 

What would you say?

Can you give me the gist of the text in a nutshell?
<bot>: My boyfriend put me in an uncomfortable situation and I want to talk about it without being accusatory. What would you say or do?