@CloudyMrs i can't imagine anything else, but that you pull in the wrong direction. With me it was always that, because the threading on the pedals is weird so that they tighten in the direction of the friction when pedaling. If the pedal is broken and had a lot of friction, then it might be very tight. This picture shows how i try to remember it: https://www.bikeexchange.com.au/blog/removing-bike-pedals-workshop-help