TS,

Your colleague will age as well later.
Most women will get fat with auntie look after their 30's.
Are you going to change partner again after that?

End the affair now before your wife finds out and leave you.

Work togteher with your wife (eg. enroll her for gym, yoga, etc)).
Also go for date again to bring the sparks again.

Love is a commitment and requires workout everyday,
Love is not just about romance & sex.

Honestly you haven't reach the "real" love stage yet.
That's when you're old/sick with disease even to the extent of your partner needs to clean you up.
Trust me when you get there, you'll regret what you did today.