Newbie problem : two thoughts at once

Hey. I am still in my first week of practicing NSR. I would say that I am a fairly high-stress individual and I have enjoyed my experience thus far. I have run into a weird situation and I'm not sure the correct response to it.

As I am repeating the syllable, sometimes another thought comes into my mind. But I continue repeating the syllable and I can hear it WHILE I'm thinking the other thought. So it is like part of my brain is repeating the syllable and part of it is thinking the thought that comes in. And lately it has been happening a lot.

I know you are supposed to "return to the syllable", but what if the syllable never left? Surely others have passed over this ground before. I can return more attention to the syllable and as soon as I recognize the second thought I don't give it life. But it does feel like I am expending "effort" to divert more focus to the syllable. These secondary thoughts have really been harassing me!

I think the worst thing is that it makes me feel like I'm not really properly practicing the technique, since the simultaneous other thoughts make me feel like I've taken the syllable for granted and I'm doing something else while I meditate.

Any advice for me on how to get past this?