Slipped it in

 I'd been hooking up with a somewhat older guy (I'll call him Raul) for a little while, and we always had a great time together - really solid personal and sexual chemistry, expectations on the same level, it was great. Because I was in a long-distance, open relationship, I always used protection with other partners to protect myself and my own partner, and he knew this.
One night, we were doing our thing and having a good time, but Raul was having trouble maintaining his erection. That wasn't uncommon with him, and it never bothered me, but it was something that both frustrated him and made him self-conscious, which I totally understand.
At some point in our shenanigans, I looked back at him inside me and realized that he wasn't wearing the condom that I'd seen him pull out earlier. I hadn't seen him put it on, but I'd assumed he had. I decided not to make a big deal of it - I knew he was tested and safe, and knew he'd probably done it so he could more easily get and keep his erection. I decided to wait, figuring he would put one on before he finished.
After a while, though, I became less sure he was going to be safe, and I finally had to mention it to him. He acted surprised, but said he would before he finished. I had to mention it again before he finally pulled out and put one on. Then we continued as before.
It wasn't until afterwards that I was truly bothered by what had happened - bothered that he'd been inside me unprotected without asking, bothered because I somehow felt like I let it happen, bothered by the nagging feeling that I'd exposed myself (and therefore my boyfriend) to even the remotest bit of unnecessary risk.
It wasn't some dramatic violation. I don't even think Raul thought he'd done anything wrong, and I suppose I can understand from his perspective why he would do it. And maybe he really did intend to put on a condom, or pull out, before climaxing. But I don't know.
I'm still seeing him. It wasn't clear-cut enough for me to feel like I justifiably can't trust him anymore, and we do have fun. I've made my position - that if he's inside me, he's wearing a condom, period - more clear after that night.
But still, I somehow feel shitty about it.