Long distance boyfriend wants me to fly out last minute?

I mentioned to my boyfriend in September that it'd be nice for me to see him when i get a week break from work in October,

..but he said no because we were beginning our K1 visa (for me to move to the US with him and get married) - once you start the visa process i can no longer go and visit him whilst the visa process is ongoing. I can only go once its approved (takes 6-9months). HOWEVER, it allows him to come an visit me anytime.

BUT NOW, 4 days before my break from work, he says he'd like me to come visit him. We have yet to send off the visa as its a lot more paperwork than he initially thought, so I'm able to go. But its last minute and i dont want to really dish out £400 on a flight because i haven't been saving money with a trip in mind. He said he'll pay half. But I'm worried my family will have things to say since I'm mentioned I'm going away 4 days before i do.

Help please!!! Im conflicted on what to do and its stressing me out.