According to the News of the World, Poynter is expected to spend at least a month in the Priory as he recovers from being dumped by the Saturdays star. His non-stop work schedule is also said to have taken its toll.
"Losing Frankie left him really low," a source said. "Dougie believed she'd be the girl he'd end up married to. He needs some time out to have a rest and get his head together."
Sandford is now dating footballer Wayne Bridge. The source added: "Seeing her with someone else so quickly came as another huge blow."
Speaking of the split in a recent interview, Poynter said: "It's c**p, but what makes it worse is getting constant reminders. When it's a regular person it's bad enough because you hear their name once in a while, or your mutual friends see them. But I see her bloody everywhere! In magazines, on the TV, on the radio. It's horrible!"