you probably were in charge when it all started, you ve always had the last say and your partner accepts it OR "ACCEPTS IT", suddenly you begin experiencing power shift in your marriage or relationship? how do you gain back the control you once possessed?

Such a relationship is unhealthy and not worth maintaining. "Control" is a dirty word in long term relationships.

Are relationships about power control or rather partnership. This sounds like a slave and master relationship.

You just have to lay down the law.
Not in negative way but in a positive way.

There are some women that you have to do that with otherwise they will run rings around you. Call her and speak to her that she isnt making you eel amnly around the house and pray that she is willing to listen.

You also have to make sure that you are working - you have all the attributes that will help u sustain that manlyness (if there is such a word).
Make sure u the bread winner, make sure u are the spiritual head etc.

i dont think there should be the talk of control in any type of relationship especially if it is the long term one, the two parties should see each other as equal partners