Ask HN: How can I learn math?

So this is embarassing: I work in HCI, and I know next to nothing about math.

When I was younger, I had a lot of problems. Ended up in a reform school, and they weren't very focused on education.

Fast forward ten years. I've done a lot of self learning... mostly statistics, but there are huge gaps in my knowledge.

Too often in my career, I've decided on a project or course of study based on my math skills rather than my passions.

The problem is, I don't even know where or how to begin. I don't know what I don't know. And whenever I try to look up a specific concept (say, the Wikipedia page on Calculus) there's so much more that I don't know that the gulf of execution is so great I end up just giving up.

Does anyone know of a good online resource to sort of start at the beginning and work my way up?

(For example, I used to also hate learning foreign languages, but discovered Duolingo and have been working on learning German every since. And it's actually kind of fun!)