Britney Spears -- Booted Ex-BF Claims ... We Were On a Break!

David Lucado says he didn't technically cheat on Britney Spears ... because his videotaped hookup with another chick went down AFTER Brit had already kicked him to the curb.

Lucado is telling friends Britney dumped him via text on August 6th. Sources close to the ex couple tell us they'd been arguing over "outside influences" -- like her conservators -- who control Britney's life ... and Spears sent him a message saying, "I'm done with you."

Lucado's cheating sesh went down the very next night on August 7 -- and as we first told you Britney's dad now owns the video of the hookup. We're told David and Brit reconciled, conveniently, on August 8.

Sources close to David tell us he wants to get in touch with Britney to pitch his "we were on a break" theory. But as we previously reported ... Papa Spears and everyone else around Brit ain't about to let that happen.