Punching while moving, Punching while being set, Punching with feet or hips? (Noob)

Ok Im in the process of learning proper punch mechanics.

I can get a nice sharp pivot and snappy punches just not reliably every-time but im getting there.

Ive started practicing footwork forward back side diagonal etc

Im having trouble putting them together.

When I punch I think turn the feet but when im trying to punch and move I start punching from the upper body or waist and neglecting my feet and hips. It just feels awkward to rotate my feet when they are busy or have just finished stepping/ moving about.

It feels easy to rotate from the waist while my feet do their foot work movement but theres no power, it has to come from my feet turning and I feel I have to be still to do that and if im still I cant advance and get to my opponent if he has longer reach or circle my opponent or retreat and punch.

So its like still I can punch great but I cant reach him, then I try to step in to reach him and I cant punch while doing that.

Whats the best way to learn/ get the hang of this?

 

Also I think its partly because I first started to punch from the waist or arm and I didnt know how to use my feet and hips properly so that old habit creeps in as well.