17weeks & 6 days question

I have a question I'm 17w And 6 days and right at 17 weeks I felt the baby move. Since Saturday my stomach doesn't feel as big or hard as usual. And without actually movement I don't know if everything is ok. I have seen so much about people not finding a heartbeat when the go for there u/s that it has me a little paranoid. Just a little curious if anyone else has been feeling this way???