Please don't apologize for posting on here, it's not an issue at all! Thank you for letting us be your sex ed resource.
There's no such thing as 'wet enough'. People's vaginas work differently, and even the same vagina doesn't lubricate the same way consistently. It's nothing that your partner should feel awkward or hurt about, because contrary to the popular myth, it has nothing to do with how turned on you are. And while I understand that you feel guilty about the way that you brought it up, it's important to remember that it was because you were physically in pain. I'm glad you're planning on having this conversation with him!
The best way to have this conversation is to be straightforward. After you apologize for snapping at him, contextualize your behavior by talking about how you were in pain at the time, and explain that that's why you want to use lube, going forward. If he thinks that your not being wet means that you aren't aroused by him, correct that misconception (this article
, especially the last paragraph, may help you). Sex shouldn't cause any kind of (unwanted) physical pain. And honestly, even people for whom penetration doesn't hurt often use lube, simply because it makes sex safer, easier, smoother, and even more pleasurable. The article I recommended to you describes wanting lube as being similar to people using a pillow during sex--it simply makes a good thing better. Does that help?