Scott Disick Back Off The Wagon ... Again

Scott Disick is fine for all to see ... he's no longer leading a sober life ... just 3 months after leaving rehab, and this could have an impact on child custody.

Scott was at Up&Down in NYC Tuesday, throwing back beers according to people at the nightclub. We're told Disick partied at Fetty Wap's table after Fetty performed ... drinking the entire night.

We're told the misstep wasn't a one-off -- Scott hit the clubs Thursday night with a flock of hot models, which doesn't bode well for any hope of reconciliation with Kourtney.

Kourtney agreed to let Scott back into her life as a co-parent, with the caveat he stay clean and sober. Given the latest turn of events, it's unlikely she's going to feel comfortable giving him unsupervised physical custody.