Moving to Spain and keeping my US job

I don't know much but I can tell you this. I am living off retirement money (social security  plus saving accounts) from the US. I pay US tax on my retirement income and on my interest earned from savings. When I transfer some of that for my living in Spain I pay no Spanish income tax because of the law (the income tax has been paid in the US). I have no income earned in Spain so I pay no income tax or social security. When I applied for health coverage I was asked if I received a pension from the US. I said yes and now have health coverage. It might be because my wife is Spanish but her income is from the same sources as mine. So she also pays no income tax or social security to Spain.