Can omeprazole cause insanely bad diarrhea?

What to avoid
Omeprazole can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor before using anti-diarrhea medicine.

Stop using this medicine and call your doctor at once if you have:

severe stomach pain, diarrhea that is watery or bloody;

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common
Body aches or pain
diarrhea or loose stools
difficulty with breathing
dizziness
ear congestion
gas
heartburn
loss of voice
muscle pain
runny or stuffy nose
sneezing
unusual drowsiness

https://www.drugs.com/omeprazole.html

Also Diarrhea is considered a very common side effect affecting up to 14% of patients.

Do contact your Dr. asap.