I wanted to get sealed/married to my bf but I made a horrible mistake?

I have been with my bf for 10 months and it's been a bit rocky. I haven't always been the most honest or faithful. I stopped this behavior in the beginning of our relationship but I was not honest with him about some transgressions in the beginning. sometime after my baptism last year I had sex with my ex bf. I felt so bad about it that I asked God for forgiveness and I never did it again. Please keep in my bf and I are both LDS. Lately, the idea of us getting married has been more of a possibility. I couldn't go through the temple with that on my heart so I told him everything and he was less than pleased which is completely understandable. He said Ill have to go through the repentance process. He also said he does't know if he can be with me anymore. On the other hand, he also said he still loves me and wants to be with me and that forgives me...he's just hurt. I thought by confessing to him that while he would be hurt, we could work through it and idk if that's even the case anymore. He's leaving to be with his family tomorrow and won't be back for 10 days. He says he's gonna take that time to think about us and get away from the situation. It hurts but he's gonna do what he needs to do. I just love him so much and I don't wanna lose him. I want to be sealed to him for all time and eternity. I told him I'm making those steps to be ready. I called around to find my new ward and I plan on making an appointment with the bishop so we can begin the process. Do you think it'll be harsh? The punishment that is.