Step by step

About a year ago me and my wife stopped trying to have our own child. The doctors tested her and me and after long time they said my wife is extremely unlikely to have her own child. She went off pill and I stopped using rubbers. My wife is very active and now that she was told she could not have babies she was depressed.
I asked my friend to help me lift her up and we started going out the three of us. Somehow one thing left to another and we ended up having a menge a trois. First we did it separately, in ours and in his his home, but recently we decided to move in and live together for a time.
As we 'moved in' things changed and we started having threesomes with my wife first just shared (we took turns) but then we started doing this in each other presence and finally we shared her in many ways, starting with one of us in her mouth and the other in her ** and now more recently we dp her too and we tried ** dp too (which turned out just too difficult).
Now that my wife was told she would not have a child we were very liberal with where we finished. Last time when we dped her I finished in my wife's ** while at the same time my friend finished inside her **. Later on the same night we repeated this with him finishing in her ** and him inside her other hole.
The point is then my wife felt sick and she though it could not be but she made that test. Twice. She is pregnant. We do not even know who of us two there is the father.
I truly do not know what to do. My wife is overjoyed. But I am less optimistic. If the child is mine, what should I say to my friend? I cannot just kick him out. If the child is his, she is my wife, and what can I do about this?
I am truly puzzled. It was fun while it lasted but now it is a headache.