Might be. I'm planning to do thyroid tests soon, because some of the things in my life could be explained by problems there, and my sister recently found out she has some thyroid problems. I understand the experience - for me, day-and-night difference was getting on SSRIs.

But it could also just be that I never started to like exercising in the first place. I have myopia since early childhood - so from the first years in school, glasses gave me logistical problems on PE lessons. It was especially problematic during team games - when I took the glass off, I was the worst player in class. When I left them on, I could play somewhat well, but I was risking breaking them when hit by a ball (it actually happened). So I ended up avoiding team sports as much as I could, and there a negative feedback loop starts (not playing made me only suck more and be less willing to play).

Anyway, thanks for the advice :).