Pregnancy dilema

I'm a 52 year old male who had a drunken one night stand with a work colleague who is married with three children.I withdrew before ejaculation.A few weeks later I heard from another source that she was pregnant and the thought crossed my mind that I could be responsible because basically I am a worrier,I can find a problem anywhere. I contacted my friend who confirmed the pregnancy .She confirmed the pregnancy but was insistent the child was her husbands.However a couple of weeks later after her dating scan she contacted me to say that the scan dated the pregnancy around the time she was with me and that she had only had sex with her husband once around that time and had taken the morning after pill .It seems the doctor has told her the morning after pill is not always reliable if taken when ovulating.She is insistent that she feels her husband is the father but I am not convinced even though I withdrew as I know it isn't reliable.She does not want to leave her husband and obviously he has no idea that he is not the father. I feel so guilty as I have met the husband however am ok with my friends wishes that she believes the baby to be his and is happy to continue life with him.I am single but am concerned about any repercussions further down the line and later in my life should her husband discover that the child may not be his.The whole situation is eating me up and affecting my work.How can I resolve this with myself?

What are you looking for? Proof the child is not yours? You'll have to figure out a way to get a DNA test to prove that. Or, you can keep wondering.

I think you're probably okay because "withdrawing" is about 99% effective. I can't say I have any sympathy for you though since I've had a similar thing happen and I know the feeling; it's very disruptive and overwhelms your thoughts. But, you did it so now you gotta live with it. Just convince yourself it's not your baby and move on and in time, it'll become easier to believe.