Backwards/backward and similar words ... Which is correct?

Maybe it shows where I grew up, but I used the following words in my drafting:

Backwards, onwards, upwards, towards, outwards, inwards, etc. (I did not use 'forwards' but rather 'forward' which I find mildly intriguing. Like, hello brain, you're a confused place aren't you?)

Should all of those words lose their 's'?

Backward, onward, upward, toward, outward, inward ...

Thanks!