Scared to repent.

Sydney
The past few years, I have made some bad life choices. I think it's because I was dating a non-member (he is a great man though. Just because he isn't mormon doesn't mean he wasn't a good person)
But there is one decision that I made that is TERRIBLE. I made it about 8 months ago and regret it every single day.
I am trying to get back into being sprititual since my boyfriend at the time (I guess my ex now) and I broke up. I feel like it's been hard to become spiritual again but I finally think I realized why.
I think it's because I need to repent. I know that I need to talk to the bishop about the things that I have done. But I am just really scared. I don't want to tell anyone my deepest darkest secrets. One of them is so terrible that I don't even know what would happen... 
I have repented to the bishop once in the past when I was a little bit younger, but this is a lot different and I am just scared. Is there a way to repent about big things without talking to your bishop? Can I just pray to God asking for forgiveness? Why must I tell my bishop?
Any advice?