If your return was accepted less than 21 days ago, hang in there. It can take anywhere from a few days to 3 weeks to go from acceptance to approval. This timeframe is unrelated to how, where, or when you filed and it isn't connected to how quickly you got your refund last year.
And it doesn't mean you're being audited — the 2018 "audit season" doesn't start until summer.
IRS representatives will be able to research the status of your refund if your return was accepted (received) more than 21 calendar days ago. Call them at 1-800-829-1040, but prepare for potentially long wait times.