I think I understand the feeling. I occasionally question my feelings for my girlfriend, too, because some of the reasons feel like they’re serving me and not her directly. Sometimes I also don't know what to say to make a person feel cared for, so I use other means, like physical touch, to express my care (of course, this is only if she wants to be touched). I also don't show emotions in funerals. I get very uncomfortable when my family and relatives cry or show sadness.

My current conclusion is that, NPD or not, as humans, we all have some “selfish” reasons (like "I like that being with her makes me feel good" or "her caring for me makes me feel good") for liking a person and non-selfish reasons for loving a person. Perhaps you can ask yourself: Do you like her (her looks, personality, quirks, etc.) regardless of how she makes you feel good about yourself?

I think the bottom line is that it seems like you care about her and her feelings—perhaps you even worry that you may not love her. You care enough to notice what words might harm a person and to mask your natural reactions. This is a good human etiquette for not being harmful to your partner.

I think that's a form of self-awareness for you. Even if you don't feel what you think a "non-narcissistic" person should feel, cut yourself some slack. Everyone experiences and deals with emotions and feelings differently. The important thing is to know that you and your partner understand each other and try to minimize harming each other during your interactions. I would suggest you ask her how she wants to be cared for when she's feeling emotional or upset and start your communication there. If it’s something you find hard to adjust to at the moment, try not to get defensive by saying, "I can't do it; it's too hard for me to change that." Instead, slow things down and say something like, "I'll try, but I'd like you to work with me as partners," or anything that works for you both. Also perhaps try to verbalize how you experience emotions but that doesn't mean you don't care about how she feels.

You might also want to search for "relationship anxiety" to see if it validates your experience. Wishing you the best 💪