Ladywolf - he is nowhere near ready to be 'tied down' to family life again.
I doubt that this 'young female friend' was a new adventure once he'd left you, I should imagine that she was in the background in one form or another.
WWIFN and Peter both give excellent advice here.
Reading your OP sets alarm bells ringing with me I'm afraid.
For me, I'd need to know EVERYTHING. Every little detail. Sex, days out, evenings out, where they went, the lot.
As hard as it is to hear, if he is ever going to be aloud back into your life as your partner, he has to open himself to you and tell you everything.
Otherwise, it will always be there, hanging over you, waiting to be used as your (or his) weapon of choice if you fall out/argue.
And you really have to dig deep to see if YOU want this man back in your life. What if this happens again? How do you think the DCs will be with him coming home.
Surely they've only just got to grips with the two of you being apart?
Why has he changed now? What's going to be different this time?
Is he only considering coming back because he quite likes being 'looked after'?
Look at his reasons for coming back, and for yours to let him.
It has to be more than that you love him. Much, much more.