I feel unhappy and unhealthy

Wanting to be single after making some mistakes in my marriage. Im a Christian, but i fell into adultery almost 2 yearsago....my husband has known about some of it since i told him out ofguilt. I have had sexual conversations with an "old friend" and he kissed me once....but i don't want to let go of him eventhough my husband says its either him or this "friend".....me and my husband have 4 kids together and i love my husbandso much! He has given me everything I've ever wanted along with forgiven me for what ive done. I have promised my husband over and.over again i wouldn't talk to this person anymore even though i have always fallen back into it. This person recently blocked me from everything...but it wouldn't be the first time for that. I just feel like i need to be single for what ive done and what im afraid ill fall back into. My husband wants to fix it, but i think he deserves better. Please no mean comments....i already know im a horrible person