It's hard to know for sure but from your post, Lavilov, it sounds like she's experiencing anxiety which she's projecting onto you. I think the important thing to remember here is that her issues are hers and not yours and that you're not responsible for her. You seem to be aware of that already, which is good (& in no way do you sound like a whiny teen to me).

Part of growing up is that we start to see our parents as people (rather than just in their role as mother & father to us) and we become aware of their frailties/flaws etc, it mightn't be that she's changed but just that you're noticing it more now (or it could be that you growing up has triggered her anxious nature).

Much like you I care about my mother, knows she cares about me, but we're not close in that we can discuss everything - it's something I've got used to over time (I'm much older than you & married with my own family btw) although I do wish it wasn't like that sometimes. Not much in the way of advice I'm afraid, but I hope you'll take comfort in the fact you're not alone.