Sherri Shepherd's Husband Warns ... You Better Not Miss Our Baby's Birth!

Sherri Shepherd's estranged husband is upping the ante on the drama over his unborn child ... warning Sherri a gig she's booked -- NINE DAYS BEFORE the baby's due date -- is cutting it too close ... and he's pissed.

TMZ has learned Lamar Sally is outraged Sherri is scheduled to perform July 19 at a gospel fest in Virginia. Their surrogate is due to give birth on July 28 ... in Pennsylvania.

According to sources connected with the couple ... Lamar is telling Sherri missing the birth would be an unforgivable sin -- especially because it's HIS first child.