I’m ashamed to say..

It finally ended and he finally decided to stop contacting me after 4 years of stalking me and pretending we never broke up in the first place. But the way I ended things to get rid of him I have to say I feel very guilty and ashamed of. I never wanted to hurt him. Me and my adhd ex were together for 6 years and my world revolved around him. Although it was constant fights and breaking up every other week he never wanted to let go.. he would create tons of new numbers and emails just to stay in touch. 
well this past month I met a man that I convinced myself I was in love with. Obviously I was not and was just imagining a different future. So I told my adhd ex to please leave me alone because I was interested in someone else. I felt like both of our worlds collapsed. After so many years of friendship we never wanted it to end this way. I'm extremely heartbroken and feel horrible for what I did to him. He has stopped contacting me now. 
Nothing happened with the new guy he obviously was not even interested in me because I had idealized it all. I think I did it all on purpose to end my relationship with my adhd ex but boy does it hurt, 

Why do these things lead to such drastic measures. For years I tried to break up the right way and he would not. Now I went to do something stupid and hurt him more than I ever wanted. I felt I was his protector for the longest. Only time can heal us now. The shame of not being the bigger person this time kills me, there's no excuse for my actions. Has anyone here had guilt like this before? Where you felt like you were the one who was supposed to have self control but failed.