I walked in on my husband kissing his male best friend- Not me ooo

I’ve been married for four years and every day of our marriage has been great.
But, for the past few weeks, my husband has been going out to meet his friend every night.
He always comes back looking more happy than he was when he went out.
He finishes work about 5pm and I get home just after he does. We usually spend a few minutes discussing what we’re going to eat that night and then he goes off to meet his friend.
I started to worry there was more to this friendship than meets the eye.
His mate’s wife is my friend too, and she also began to get suspicious about these constant outings.
Then three days ago I came home later than usual from work.
I headed straight to our bedroom to change out of my work gear and walked in on my husband and his friend kissing.
I was so shocked I instantly ran to my car and drove to my friend’s house, and told her what I’d seen. She was shocked and angry, too.
I still love my husband, but now I don’t know if he loves me back.
What can I do for him?