if a bill is passed in the house but not in the senate, does it have to start all over again in the house?

That is generally how it works. I could create a hypothetical situation where the Senators just did a motion for reconsideration and adopted the exact bill they turned down, but typically it at least needs changes to get votes after that, so the Senate Bill then wouldn't be the same as that in the House. It would go to committee to come up with a compromise and the House and Senate both would have to vote again, up or down.

It would really have to start over again in both houses because it doesn't become legislation. It has to be approved by both houses and then sent to the Presidents desk to be signed.