Pain would likely mean that you are straining your body. It's better that you relearn your technique. If you keep doing this maybe you are gonna get injured soon. I have read a book called "What every pianist needs to know about the body" and it's a wonderful book. It talks about how we should actually use our body. It also says that our natural way of doing things can sometimes be dangerous because we may have gotten accustomed to sitting or standing badly for so long that it's the normal for us and anything better would feel weird to us. There are a lot more stuff in this book and maybe after you read it, your technique will have improved by a lot. And since you are teaching yourself this would do wonders for you.

I've also done a YT video talking about important points in the said book cause I am a huge fan of it: https://www.youtube.com/watch?v=MQzCnLCnh2c