How to deal with past unintentional and unpunished plagiarism?
First, it is unreasonable to blame your instructors.  For what reason?  If they had done something years ago, you wouldn't feel bad now?  Probably it was not obvious to them that you had plagiarized.  (Plagiarism can be more obvious or less obvious, depending on many factors.)

Second, people make mistakes in life, and not all mistakes are fixable.  You just have to do your best to be honest and correct now and in the future.  You might consider contacting your old professors to let them know what you did, and that you now realize it's plagiarism and that you are sorry.  If you need to do this to feel you are "deserving" of your situation, you could also redo your projects and send them to your old professors, but this is not ethically necessary.  Who among us deserves the fortunes granted us?  Not I.  I can only appreciate them.