Heavy lifting and stomach pain do not normally go hand in hand or nobody would ever do it. It's possible you lifted too heavy before you were physically ready.
Weightlifters and Hemorrhoids: Lisa A. Perryman, MD, FACS, FASCRS: Colon and Rectal Surgeon
Lower Back Pain From Deadlift: Form, Prevention, and Recovery
Pueden las lentejas causar acidez estomacal? / Enfermedades y
Can Heavy Lifting Give You a Hernia?: Surgical Associates of North Texas: Advanced Laparoscopic Surgeons
Know The Difference: Abdominal Strain vs. Hernia
The Valsalva Maneuver in Weightlifting
Why You Have an Upset Stomach After Workouts
Deadlift Back Pain Prevention and Treating an Injury
Deadlifting Can Cause A Herniated Disc - Dr. Kevin Pauza