Graduation and Gradual Descent into Chaos

So, I just finished my grad program a month ago. Got the degree, landed a job at this tech company downtown. Should be happy, right? Well, not really because I'm still stuck on my last relationship. We were together for three years, same department, same interests, same everything. We broke up six weeks before graduation day, and it was one of those messy break-ups where you're both pretty sure you still love each other but you can't quite figure out what's wrong. I moved into my own place right after the breakup, thinking some space would help. But then I started seeing this coworker who I'd always had a crush on, and things got complicated quickly. We hit it off romantically in ways that weren’t expected at all given our past. It felt freeing, like starting fresh without any strings attached. Fast forward to now, and I'm realizing how much I've actually missed my ex-partner. Her name is Jane, she's thirty-two and has been my closest friend since before grad school. The sex with her was always great, no matter what kind of mood we were in, even on our worst days. With my coworker, there’s chemistry but it feels different somehow. I'm not sure where to go from here. I've been trying hard to just focus on work and move forward but old habits die hard, especially with someone who knows every single detail of your life. It's a weird feeling, like you’re in the same boat as before graduation, except now there’s also this new person who keeps sneaking into my thoughts. So yeah, here I am. Just venting to get it all out. Maybe if I type it out, I'll feel better or something.