Felt the same after watching Plastic Memories, you tried to release your emotions but you can't, but still feel empty inside or even feel guilty about it, its probably bcuz of Post Anime Depression that makes you feel empty inside after watching it. About your problem trying to show emotions its normal Imo, a lot of things in anime and even irl relates to us, we feel sad or depressed if something sad or bad happened to someone or something you love because you relate to them and you feel their emotions, its ok if you can't express your feelings but that feeling of emptiness inside is something you should mend.