Mathematicians who started late, similar to my situation?

Let me tell you that it's not too late to enjoy the field of mathematics. I too went through a circuitous path of getting into mathematics. I was extremely lazy in high school, had mediocre SAT scores and had no idea what a math competition was. I was a business major for undergrad and studied finance. It wasn't until after I graduated that I made friends with a guy that had been a math major in his undergrad. He eventually convinced me to take the honors calculus series at a local community college and promised he'd help tutor me. I was fortunate, my teacher there was a PhD student at a local well known college and took a liking to me and became somewhat of a mentor. I was a little neurotic and became obsessed with math. I ended up quitting a full time job, moving back in with my parents and then taking classes at the local university (you could pay and take classes as a non-matriculated student). I did this for two years, taking only math classes and then eventually applied to their MS program and was accepted. I have since scored in the top 97% percentile of the GRE general math, and published one paper with another in progress. I'm going to take the Math subject exam in the Fall and apply to Phd programs.

So, will I ever be a math wizard... no. But do I love mathematics, yes. I share this with you so that you know, there are people out here that started even later than you and are happy they did.

I'm not sure where you are in your education, but working problems is one of the (if not the) best thing you can do to solidify your foundation. The book that made me want to become a mathematician: http://www.amazon.com/The-USSR-Olympiad-Problem-Book/dp/0486277097

Don't know if this helps but if your aim is to enjoy mathematics, and if you are enjoying it, then that sounds like success to me!! Hang in there, you are not wasting your time.

I can relate to your feeling of being intimidated by other people that seem so far ahead of you, and the sense that you might never be able to catch up. Piling on top of the natural, unprompted feelings of inadequacy, from time to time you will run into professors and/or other students who are into what I've heard called "mathismo"--deliberate effort to prove "I'm smarter than thou". Such things are a fact of life. It helps to put a name on it--"that's just mathismo, I'm going to ignore it"--because you can realize that focusing on this will get you nowhere and in fact will impede your progress.

You don't need to worry about whether you'll be able to prove important theorems or whatever. Not yet. You have only seen a tiny little bit of the field right now. There is so much you can do with math. One thing that sticks out to me, based on your description of yourself, is actuarial work. Great pay and high job satisfaction, and it really fits with your description of yourself as doggedly going through the basics until you understand it really well, etc.

But that's just one possibility. Math is a gigantically varied subject--"set of subjects" would be more appropriate. You are very likely to be able to find a niche that you enjoy. If you like what you are doing so far, I would say that you should keep doing it. Maybe something you end up doing will lead you in another direction eventually. That's not failure, that's just life. If you are really making sure you understand it as you go, you'll be able to use what you learn in math for the rest of your life even if you switch to another major.

My advice is "Onward!". Keep at it, and if it gets to the point where you just aren't enjoying it any more, do something else at that point. There's no point in worrying about the unknowable--you can't know right now what you're going to think about upper level math, because right now you probably haven't really seen anything like it. School unfortunately just doesn't give people a very clear idea of the vast scope and depth of what mathematics has to offer.

If this is what you think you want to do, don't let anything--whether it's an inadequacy in your past or a current deficient comparison to your peers--stop you. At the same time, be honest with yourself in realizing that you can't, at this point, really know where it's going to lead. Mathematics is an awesome universe with tremendous opportunities for exploration. It's a great place to be looking around and taking things in. Enjoy the journey.