When was the last time you felt guilt about something, as in that emotional pit you noticeably feel in your stomach when you have done something wrong towards someone?

All the time for the past few months, I went through a break up because of my own stupidity, but recently she wants to talk again, but lightly, and with the fact that nothing romantic is possible. I tried talking to more people and even one I caught a few feelings for but I realized I didn't actually like them and it just made me realize how great she was again. I just constantly feel guilty cause I want to try again but I know I don't deserve another chance, and other parts of my life with me trying to find a new place to live, a new job, dealing with college classes that I didn't really wanna do. I just feel like a constant failure when I had so much opportunity. Got depression meds, and they worked for a while, but they are working less and less now.