Should I tell My Husband That my Sister is Actually my Daughter?

I currently live in the UK and I am married to the most loving guy that I can ever think of, trust me I have been around so I know the attribute of the word “most loving guy” though all is not perfect at the moment but the dilemma now is that I am stuck between my mother, myself, my husband and our four months old baby and I really think I have made a very serious mistake courtesy of mother and all her advice.
I have known my husband for close to 12 years and of which have been married now for 2yrs. Unknowingly to my husband I had a baby for my secondary school love just after I finish my SS3 exams in Nigeria, and with the help of my mother we were able hide this from everyone apart from my immediate family because my then boyfriend denied the pregnancy and my mother did not want word to get out the her most precious teenage child has become pregnant.
To cut the long story short, I gave birth to my first baby girl in a very small town in one of my mothers numerous friend’s village, and my mother flew me abroad shortly after, and my baby was given to an Orphanage home near Port Harcourt run by again one of my mother numerous friends. later my mother adopted my daughter and she does not know that the one who adopted her is her grandmother.
Please readers tell me what I should do, should I tell my husband that the little girl that I told him was my younger sister in Nigeria is my daughter or should I keep mute, please don’t forget the first daughter does not yet know that I am her real mother.
Please honestly what should I do.