I worked with a [F] colleague for around 10yrs, I've since moved to a new job at a different company and we are still connected via social media

For background I'm in a long term relationship with my partner [F] and we are very happy together.

My old [F] colleague was extremely chatty with me when we worked together (nothing happened between us 😉) however she is stunning, athletic toned with small shaped boobs and wore (what I thought) attractive business attire.

On her socials she has bikini shots, which show off her incredibly toned body, and even 'pokies' which shows off boob shape even more. She recently turned 40 and her birthday dress was a gorgeous ball gown.

Even though I'm happy with my long term partner I'm finding myself thinking of my ex colleague during sex, and even occasionally wanking (jerking) off to my ex colleagues bikini shots.

My ex colleague is married with school age children.

What's the saying 'always wanting something you can't have'

Anyone else been in the same boat with fantasing about a colleague?