There's a tendon that runs from behind the toes, across the arch, under the heel and up the back of the leg. Shortening of this tendon is what causes fallen arches and heel spurs.
Sitting at a sewing machine or sitting anywhere can be horrible on those tendons. Try laying or sitting and putting your legs straight out in front of you and pull just your toes toward your body. I do this several times every morning before I get out of bed, while sewing, at the computer, watching tv, etc. It will help tremendously. Just remember, it didn't happen overnight and it will take a long time and a lot of constant effort to reverse it.