I did something a little stupid. What now?

I'm 19 and I've only ever been with one guy sexually, and that was the guy I lost my virginity to. He was also a virgin.

I've been seeing a new guy for over a month now. We haven't had sex yet, but I did go down on him. He didn't finish in my mouth though. Anyway. We've talked a lot about sex before and previous partners. He's told me that he has had 26 or 27. I've had one. We talked about it and my nervousness because of his experience and my lack thereof and all that. But I forgot to ask him if he has been tested for STDs/STIs. I know this was a big mistake. Especially since I've went down on him. I've just never had to ask that before and I'm quite new to "adult dating" I guess you'd say. But we've been very open about our sexual experiences and pretty much everything else, and I do trust that he would've told me if he had something. He also mentioned before that unprotected sex has always been out of the question for him. It's not like he's some shady guy I hooked up with. But now I feel like it's awkward to ask since I've already went down on him before. How should I go about asking him now?