Everything feels like a mistake to me, help?

I don’t know what’s going on with me, but everything I do… I seem to regret doing and it feels like a mistake to me. I just started dating a guy two days ago, but I’m not happy about it. He’s a sweetheart, but I’m regretting the relationship. It’s not the only the relationship. I feel horrible when I switch my normal routine. I know it’s because I’m starting to change things around in my life, but if I’m not feeling right about anything and it’s only making me depressed, shouldn’t I just continue on the path I was on? Should I just force myself to get through the feelings I’m feeling now? I have no idea what I’m supposed to do. I know and know for a fact that I can’t wallow in my pain and past heartbreak for the rest of my life, but it seems impossible for me to get around. I feel wrong about everything and I’ve been thinking that my life is pointless. I feel like I have nothing to live for.. Help? What am I gonna do when I feel like the happy, life-loving ducky is gone?