Nexium is a drug surely brewed by Satan himself.
It alters digestion and acid production including receptors (most likely through fluoride poisoning), coming off this drug takes weeks.
Almost all stomach acid or gas issues can be corrected by using the scdiet or Atkins. Sure there may be some parasite issue but the crux is a damaged intestine. See scdiet.org and work on correcting your ileo-cecal valve.