Advice please

Where do I begin my story Hi my name is Darren. I am 25 years old and recently decided to contact my biological father, a man I have known about all my life but not had any contact with since i was 2. I am not sure why or when he and my Mum decided that he would not be a part of my life. I was raised by my Mum and my dad (who i call my dad) whom she married when I was 2 and half, who later adopted me after the marriage. I always had a sincere interest in contacting my biological father someday but was honestly afraid of rejection or hurting my dad, after all he was doing a brilliant job raising me, giving me everything I wanted. I toyed with the idea of contacting my biological father year after year in my teenage years, until at the age of 21 i did start looking for him,i stopped looking when i saw the effect it was having on my mum,however I knew it was only a matter of time until i had to start looking again to satisfy my curiosity,... aged 24 i had my first child (a boy) and suddenly started asking questions in my head about my natural father (i refuse to call him dad because to me a dad is someone who brings you up not just create you),I didn't want to hurt my mum but realized this time, I was doing this for me and if my biological father rejected me I could deal with it....... I hoped, i did a little bit of digging using common sense and after a little over 20 mins online i had found him (on facebook) i didnt send him a message as i wanted to talk to my mum and dad before potently opening a dirty can of worms after about a week i sent him a message and was quite blunt with what i said,he replied and we started communicating every other day roughly, this has been happening for about a year now .....however he threw a "spanner" in the works by saying that he might not possibly be my father as my mum had told him (apparently) that he might not be, my mum and dad have always been upfront and honest with me and when i turned 18 they let me read all the relevent court documents and everything they had told me as i was growing up was confirmed in the documents so it came as a bit of a shock for him to say that he wasnt sure i was his son. we are still talking on facebook and have arranged to meet next month for the first time in 23 years, i want to meet him but am also concerned that he may be using me to upset and annoy my mum,my dad is being very understanding and supporting me 110% and has offered to pay for my ticket to meet my natural father but i dont know what to do for the best , any advice would be gratefully received Thanks in advance