Is this through HomePath? If so, your agent will be able to tell you the status. There is no notification if your offer is rejected; the agent needs to log in and check the site. They will only tell you if you're countered/accepted, or when there are multiple offers. If this is your second offer (presumably on the same house), then apparently you've gone through one multiple offer round and have revised your offer.
Fannie Mae does whatever it pleases! Typically they'll answer in 3-5 days, but there is no guarantee at all. Prices are all over the place, and it's not uncommon for houses to go over list price.
They will typically counter the best offer, and negotiate with that buyer until they reach agreement or impasse. That *might* be what's happening here. If your offer was not the best, Fannie Mae could be negotiating with the other buyer, waiting for proof of funds or other documents, etc. If they haven't rejected you, you're still in the running.
If they accept another offer, the status will change to rejected, but your agent will have to check it to see that. If they reject the "first" offer, they might do another multiple offer round (e.g., if they got other offers in the meantime), in which case you'll be notified. Or your offer could move into first position, in which case you'll get an acceptance or counter.