Should I have been paying taxes on American stock dividends?

Listen, I get confused and overwhelmed with taxes and finances and it makes me want to curl up and cry. I should have asked for help ages ago, but instead avoided it.

Situation: Canadian citizen with American stocks from a previous employee share program (from within Canada). I only ever filed Canadian taxes. I left that job, so no longer contribute to buying shares or have done anything to those accounts; but they do obviously fluctuate and I get emails saying anywhere from $15-30 interest/dividend has been paid. I pay almost zero attention to them. I am now living in the U.K. When I used to file my Canadian taxes, I never declared any foreign investments. I never received any payments to my Canadian accounts from those stocks and never sold any shares – so I never considered that was potentially required. In the back of my mind I’ve been worried I’ve done something wrong and owe taxes for all those years. But I have no idea how stocks and dividends etc work – might as well be a foreign language to me. Again- this was all done and set up through my employer – I had nearly no responsibility other than saying yes I would like to contribute.

I’ve tried to look around and log into my accounts to help me understand. When people talk about a brokerage – my stocks are held with E-Trade (if that’s right?). So I suppose the “dividends” I get emailed about are just paid into the account there that shows my whole balance? I can see there are tax forms there – which makes my heart sink, and hence posting for advice on Reddit.

Can anyone be so kind as to try to put this in laymen’s terms for me to understand if I need to – and how to – pay back tax on previous years?? (And is this on my Canadian tax returns?) thank you so kindly in advance.