eat away at sb

eat at sb AND eat away at sb (bother, annoy, cause feelings of guilt; to make someone feel more and more unhappy or worried; to make someone feel very worried over a long period of time) — {о мысли, чувстве, переживании} мучить, беспокоить, тревожить, грызть, терзать ; не давать покоя; делать несчастным кого-либо
If something (a memory or bad feeling) is eating (away) at you, it means that there is an unresolved situation, and that you are unhappy leaving it unresolved and are distracted and annoyed by it —что-то (воспоминание, вина, ревность) гложет, на дает покоя.

Example 1: I need to apologize to him. I know I hurt his feelings and it’s been eating at me. — ... это меня гложет.

Example 2: Though Alice and Mike are happy together, there’s something that’s been eating at Mike.

Example 3: You could see that jealousy was eating away at her.

Example 4: The thought of mother alone like that was eating away at her. (LDOCE)

be eaten up with/by jealousy/anger/curiosity etc to be very jealous, angry etc, so that you cannot think about anything else

what's eating somebody?
Used to ask why someone seems annoyed or upset:

Example 1: What's eating you today? — Что тебя мучит?

Also
weigh on sb (to bother you or cause you worry)

Example 1: .....There’s something I really need to get off my chest. It’s been weighing on me for so long. — ... давно терзает (мучит, гложет, тяготит) меня.

Example 2: .....All the work I have to do tomorrow is really weighing on me. I can’t wait to get up and get it done. — ... висит надо мной.