feel guilty
To feel ashamed and remorseful about something. Thanks for being so nice about everything, but I still feel guilty about interrupting your date. I know Jen pretty well, and I think she feels guilty about upsetting you.
feel guilty (about something)
to feel that one is to blame for something; to feel intense regret for something that one has done. I feel guilty for forgetting about your birthday. You shouldn't feel guilty about the accident. It's not your fault.