My corn doesn't digest at all, heartburn even when not eating. what could this be? it just started.

GI issues: Corn is known to be poorly digested even in healthy individuals, so this may be somewhat normal. Heartburn is, however, not. Although, more history is needed to arrive to a diagnosis, you may try diet change - avoiding foods known to cause/aggravate your symptoms. Simple over-the-counter acid reducers - omeprazole, once to twice daily or ranitidine twice daily before meals may be tried x 1-2 weeks.