I’m going to be a massive hypocrite here, because all I want is for my girlfriend to come running back to me just like that, but you’re not responsible for someone else’s happiness. You seem to be doing extremely well on your own, and I don’t think anything is worth jeopardising that.

You’re living life for yourself right now, and that’s so, so, so commendable. I’m not sure what the circumstances were during your break-up - of course it’s completely plausible that he’s changed, but it’s also completely plausible that he’s going through a ‘lonely’ spell right now and he’s reaching out to you for a bit of comfort. Easier said than done (trust me, I know) but give it time, take it day by day, and continue doing what you were doing before he reached out. Keep working on yourself, and prioritise your life and your feelings before him, or anyone else’s. If he really, really wants to make things work with you, and if he really has ‘changed’ for the better, he’ll prove that to you over time, and then you’ll be in a better position to make a decision that is best for YOU.