I would speculate and say that the time apart from your ex isn't the problem.
The time that you have been enjoying yourself is more the problem.
Living alone is "ok" but while living alone, do you find yourself laughing out loud (often)? Find things very intresting that you want to do it again? I would speculate and think - possibly not. You are happy being alone but you could be much happier.
Living alone doesn't let you enjoy life to that exiting extent (usually) unless your the sort of person who is a "get up and go" sort of person. Exiting and spontaneous, full of adventure.
Living alone does allow you to be shielded from some upsets that a relationship might cause. You are able to control your environment more while being single and alone.
Thinking back - you have your ex (that you felt close to) to remember and nothing to replace that happy (and close) memory with.
The new person in your life has been something new after the "suspended" life you lived for the 2 and a half years before, and the change is perhaps a bit of a disruption.
6 months of weekends. 2 nights week and 4 weeks a month. = 60 nights add 24 nights during the week and you have 80 odd nights of time together. I am sure that the time together is sometimes shared, perhaps by a drastic half. You are just starting to experience a few intresting things in your life now and comparing the new experiences to your past makes you want what you had - which raises the question - can you make a prediction in your life using what you know about your new man and think yourself into having a good close relationship with him?
If you can't see something in your life growing and improving, based on your past experience.You might be to fixated on trying to mirror your past on your current new development (relationship) or it might be that you don't feel that this relationship is going to be as good as you want it to be in the future.
The good thing (and you should consider it a strength) is that the relationship is building slowly. A slow built relationship has a better potential to go further and be stronger.
Based on your replies, you would have to take account of what you know now and imagine what you would want in the future, then decide if your future is going the way you feel it should.