Keep your feet together. Make your goal to make contact skate-to-skate ("clap" with them slightly) as much as possible. Push - bring feet together - push with other leg - bring feet togeter. You just go straight without pushing? Feet together, skates touching. You practice lemons? Legs wide - legs together "clap" - legs wide - legs together "clap".

That will help you with controlling your center of gravity left-right-wise. Now, your center of gravity is always between both legs. Good skaters can shift center of gravity from over-left to over-right leg freely and use this all the time. Beginners tend to keep their feet wide because it feels safe - you won't fall to the left/right easily. You need to break this comfort zone :)