When did you feel your biological clock ticking?

I have really been noticing lately that my desire to become a mother has been much stronger than ever and the feeling has lasted longer than it usually does. Every once in a while, maybe once a year or so, I get a little motherly urge. I don't know if it's because I'm planning my wedding and actually starting to see my future with FH as a family, as opposed to just a relationship, if that makes sense. I'm 26 now, just really started my career over the last year as an attorney, and I know that I am not ready to have a child now. I will be 27 when I marry, and really figured that we would aim for having our first child at 30. I know that most likely within the next 2 years, some colleagues of mine and I are planning on starting our own firm, which will be a major life change at around 28 years old, and I know that it will be very difficult to balance not only a career, but running a law firm (with the help of others, but still...), and a family.

I just can't shake this feeling, even though I know that I am not going to have a child before I get married and probably not within the next few years. I am afraid it's going to consume me, that's how strongly I've been feeling it. I don't really talk to FH about this, because it's just not something that I can explain, and I know that just discussing the possibility of having kids within the next 3 years freaks him out right now, so I know that he's not ready.

For those of you who have felt the same thing, or really noticed when it was that your 'biological clock' (I really dislike that term) started ticking, how old were you, or where were you in your life when you noticed it? For those of you who didn't follow the little voice in your head, how did you make it go away until you were ready or until a future point when you might be ready?

Thanks!