Learn English – word for emotion that’s not quite to envy or jealousy

Jealous is defined as "very watchful or careful in guarding or keeping," and resentfully envious. Envy is defined as "a feeling of discontent and ill will because of another's advantages, possessions, etc.; resentful dislike of another who has something that one desires." Jealousy has stronger emotions attached than envy.

Is there a word for feeling sad and missing something you want to be a part of? For example,

I'm not feeling jealous, I'm sad and feel like I'm missing for something. I feel _____.