<human>: I dated a really sweet guy through college (for about 3.5 years) and then broke up with him after I graduated because things weren't working out. This was about a year ago. Long story short, he was great, but we had some fundamental compatibility issues that surfaced only after I became more and more financially and professionally independent (from my parents). About nine months ago, I started dating a school friend (know him for ten years now), and things are going great. We are compatible as people and I feel as though our relationship has crossed the initial stages/milestones and has become quite meaningful. That is to say, he is important to me and I want things to work out between us. 

The relationship with my ex came pretty close to turning into an engagement... and we spoke often about ending up together. It was a super serious, big deal to the guy, perhaps more than it was to me, and I'm not sure he has moved on. We are in touch because we did have a great friendship, and I make sure our communication is friendly and polite and doesn't lead him on.

My current boyfriend does have some concerns about my correspondence with my ex (as is natural) and we've spoken about whether it would be better for my ex to know that I've moved on.

Should I tell my ex that I'm seeing someone new? What is the best and gentlest way to do this? (We don't talk on the phone, we just text).

Summarize the given text in a few sentences.
<bot>: broke up with super serious bf a year ago, now seeing someone new, should i tell my (now) ex bf that I've been seeing someone for the past 9 months? How to not be a bitch?