Blaming the fact your good at math for your lack of confidence in writing is, sorry if this sounds harsh (I don't mean it to be), pathetic.
You can write well if you want to. That's all there is to it.
Why am I bad at math? Because I don't devote enough time to it, and personally, I don't have the will to devote time to it (at least not now).
If you have the will to write, you can.
Although technically speaking you can't succeed in literally anything if you try (such as swimming to the moon), writing is one of the many things you can.
Will you be the best writer? Maybe, maybe not. But you can be pretty freakin good.