Most of my life I've found myself feeling like a disappointment.
Have you tried talking about what makes you feel like a disappointment?
Yes, but it didn't really help.
If you feel like a disappointment, it would be good to get to the root cause of your issue. Even if you've tried talking about it before, you should try to find a therapist or someone who can help you through your feelings and give you a different perspective.
I'm not going to tell him that he's the problem in the relationship. It's my fault for making the relationship toxic.
You need to do whatever you can to not feel like a disappointment. It's honestly really bad if you feel low on yourself all of the time, and you'll feel regret later in life if you allow it to fester.