Thanks for the query.
After delivery it will take sometime for regularization of hormonal
levels and for onset of periods.
Some women may conceive during this period without their notice.
But as you had negative pregnancy
test and also periods the chance of pregnancy is very less.
So the feeling of moving something maybe just psychological.
If that persists better to go for ultrasound
once, by watching empty uterus
in the monitor you may come out from that feeling.