Miscalculated stock/loan basis for S Corp and thus didn't take the business loss on personal return

I started my S Corp in 2017, had a net loss which I took on my personal returns (had enough basis).

In 2018, company again had a net loss but I miscalculated my basis so as per my miscalculated basis, I had to suspend about 90% of the loss.

Now for my 2019 return, do I apply the suspended losses or do I file an amended 2018 return and apply the losses in the amended return?

The miscalculation: the miscalculation is that, instead of transferring large amounts of money to my business account, I had paid multiple large expenses with my personal card. In my accounting I classified this as shareholder loan but when calculating basis I only looked at shareholder capital (forgot to look at loan)

Thank you!