Charyl, those sticks are only good for a limited time. there's usually an expiration date on them. The date is for an unopened bottle, however. If you've opened them they last about 6 months. Best to keep them someplace cool and dark (I store mine in the fridge with the butter )

Eventually you'll be able to tell you're in ketosis just by the taste in your mouth. There are other signs, loss of appetite, different smelling urine but the fruity / sucking on a bandaid taste in your mouth is the easiest to detect.

HTH
Nat