I'm a 32-year-old man; I spent the majority of my 20s in a couple of long-term relationships and so never really got used to "dating." After some introspection, I realize that I've got some work to do on myself before I get into another serious (read: exclusive) relationship; in the meantime, I'm enjoying dating casually.
The problem is that I seem to give off "boyfriend material" signals. Case in point, for the past couple months I've been seeing a 25-year-old woman once or twice a week. The explicit understanding is that it's casual and we're not exclusive; reading between the lines I think she's probing for more. Female friends have assured me that women do not do things like buy little presents for or bake a homemade apple pie for a guy they want to stay f*ckbuddies with, which this woman has done for me.
She hasn't expressly started the "where is this going?" conversation, though, so I guess my question is: at what point does it become my responsibility to do so if she doesn't? I'm happy with the status quo so I have very little direct incentive to do so, but I don't want to lead her on. If she wants a boyfriend, she should absolutely have one; it's just not going to be me, for reasons that have very little to do with her and are largely out of her control. And I'd hate to think that she's stopped looking for one because she thinks I'm going to become one.
As an adult man, you know what behavior sends boyfriend signals. You're not stupid. So for starters, stop doing those things. If you've told her directly that you have no plans on getting into a serious relationship with her, then that's explicit. Not explicit is saying you're just looking for something casual. There's a lot of wiggle room in there. Two dates a week is not casual to me. That's pretty consistent. Also understand that, by seeing her so frequently, you are most definitely in a relationship with her. You might not be exclusive, but you're in a relationship. So, exclusive or not, you do have some responsibility for her feelings. You're trying to rationalize your way out of disrupting the status quo because it works for you.
It sounds like you enjoy having a girlfriend, you just don't like being a boyfriend. You appreciate the attention and affection being shown to you. It's the reciprocity and obligation you don't want. That's not fair, nor is it kind or mature.
I agree with your female friends: writing cute notes and baking for someone is not something you do unless you're really into someone. If you suspect she's sticking around waiting for things to become more serious, then it's time to speak up. There's no milestone that needs to be met for this conversation to be had. As long as you're playing along - and we both know that you are - she's going to think there's hope that things will progress into a full-blown relationship. It sounds like whatever "explicit" boundaries you set were either ignored or not as explicit as you thought they were.
If you truly don't want to lead her on, you'll speak up sooner rather than later. Yes, it might end things, but that's the best course of action for both of you. If you continue on with this charade, not only will she be deeply hurt but it will impede whatever self-improvement you're trying to achieve. It's hard to be become a better person when you're acting like a selfish dick.
You know what the right thing to do is here. Please do it.