My best friend's partner confided in me?

So my best friend is getting married. I am particularly excited because since high school she was dating that guy and I was telling her that I will be her bridesmaids etc..
after 10 years of togetherness, it's becoming true. However, the other day we were returning from her surprise bridal shower on our way back I was telling them about a story of my aunt, how she does not respect her husband. I saw my friend kissed her then fiancé's hand. I did not think much.
so he dropped my best friend first, just as my best friend was getting off he asked me to come sit infront in the place of my best friend.. I was surprised because he said that and that too infront of my friend.
I went to sit infront. When we were on the way to drop me, he told me whatever I mentioned in my aunt's story actually applies to them. After 9 years of relationships he wanted to break up due to lack of intimacy between then.
i was shocked! I did not know that they had issues. However my friend decided to get married and promised her fiancé to tackle the intimacy issue between them. He also told me he will proposed to her intimately as they were getting married on Wednesday. I gave him a few tips as he seemed nervous.
Since that day, my best friend's attitude has change towards me.
What disturbs me is that it was as if I was giving a moral to my best friend during that trip.
my best friend matched me with a groomsman knowing that I like a guy but is unaware that things are pretty serious between us.
should I avoid my high school boyfriend? I don't want to let her know that I am aware of her personal matter and that her then-fiancé (now husband) confided in me, it will cause more harm than good.
My best friend's partner confided in me?
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