Custard hates me

I officially can't make custard for love nor money.

I don't know what I do wrong, but it always ends up burning and sticking to the bottom of the pan and tasting weird. I kept stirring it and turned the heat down really low, but it still burnt.

I had to use a heady concoction of Hob Brite, Cilit Bang and boiling water to scour the pan clean. So irritating!