Workplace issue with my boss

I had a fling with my married boss starting 2 years ago. It continued for about a year. It was on and off as occasionally he would get that stab of guilt until and he almost got caught by the wife. Ever since we agreed to stop fooling around things at work have been awkward (It's been about 13 months now).
He's fine when giving me tasks to do both over the phone and in person, but if I was to be in the same room with him, I feel tension and there's an awkward silence. If he is standing around and I walk near him, he would turn around and walk away. There's no eye contact with each other when walking by. We don't chat but he will with everyone else.
I too am behaving the same way. What do I do?