I am so scared

I have just found out that my husband of 8 years has cheated on me in my home with one of our close friends whilst her partner, my husbands good friend, was asleep in our spare room and I was out of town for 2 days. I found a condom in his pocket and the evidence in our rubbish. He originally denied knowing anything about it, but after I spoke to her partner all was confessed. We, I thought were in a strong and happy relationship and I had no concerns that he was unhappy. 2 years ago I got MS, lost my business,finances, health and dreams. We got through that, started new plans and were battling through. But now I find out he has cheated and betrayed me. He said it was a huge mistake and is terribly sorry. He said it was a stupid thing to do and he does not know why. He said she offered about 2 years ago and he turned her down. They were talking about her affairs and how she liked sex and he decided to ask her if she wanted to have sex. What do I do with this and how can I move on. I am still very sick with MS, I have now lost my best friend in the world who was supposed to protect me. I am now so insecure and scared I don't know what to do. Should I give him another chance, or was he telling me he wants out now.

He said it was a huge mistake and is terribly sorry. Give him one more chance.