Experiencing difficulties with oral intimacy.

I'm a 22-year-old man in a relationship with a 19-year-old woman. To give you some context, I'm recently out of the Marines, and my cousin's wife introduced me to her coworker. This is my first relationship and her second, and we've been together for almost five months. I lost my virginity to her, and we've been intimate several times since. Overall, things are going really well, and I feel happier than I ever have before. However, something happened tonight that got me thinking. She’s currently on her period but still wanted to engage in oral activities, something we've done before without any issues. Still, since I can't reciprocate while she's on her period, I found myself feeling a bit turned off, and we ended up just cuddling. She reassured me it was fine and not to worry, but I can't shake the feeling of guilt. If the roles were reversed and I had erectile dysfunction, I'd feel self-conscious too. I want to work through these feelings but am struggling to understand why I'm feeling this way and how to address it. I’d appreciate any advice or insights on this, as well as suggestions on how to improve the situation. The night went well overall, and I truly value our relationship. However, I don’t want to disrespect her privacy by sharing too much, even in an anonymous context. Any help would be greatly appreciated. Thank you!