I'm thinking very high level here and haven't seen if it works... but I'd do something like the following:
On clicking Back:
1) Use a Index Of Item In Collection to see where you are
2) Use a Get Item By Index to navigate to (index - 1)
If you ever need to recover where you were when going back through the loop, you'd have to also do the following with the steps above:
3) Store each index that you've navigated to s.t. the For Each Item in Collection ignores it in the next step.
4) Come back through your collection via For Each Item In Collection, but skip any item you've preciously navigated to (via some Compare Rule against stored the index collection above)
This, of course, assumes that each time you go through the For Each Item In Collection, you march through the collection in the same order each time.
Hopefully this helps.