Hi,
I am sorry to hear that your son was separated from you for those long years, but at the same time happy that you found him.
Fear of rejection is normal human emotion, everybody feels this emotion at some point in life.I do not know under what circumstances and for what reason he was separated from you,regardless of reason you might be blaming yourself for his separation from you and are scared that he might blame you.
Reality is we are humans we go through so many life experiences, some are good, some are bad.
we loose our power, self esteem and self worth to bad experiences and gradually develop fear to face difficult situations might come in our lives and avoid taking risk. Good news is that power and confidence can be regained with the support of loved ones and counselling.
Life throws so many challenges at us its up to us how we face those challenges, either avoid those challenges or face with empowerment and become strong.
Your son is 45 years old now and you do not know how would he react towards you and are scared that he might reject you.
How would he reacts towards you it depends on his personality, what is he told about you while raising, what he believes about you, he might not have as strong feelings as you have because he was separated from you many long years and do not have that connection as mother or child develop with each other.
No matter how he reacts, you should not be afraid to contact him you are his mother, gave birth to him and love him so much. By holding yourself back you miss out happiness and excitement your son might bring to you.
Initially he might not have strong feelings but over the time as you would be in touch with him, he might develop those feeling and would bond with you gradually.
I tried to answer you based on my understanding but you choose what your heart tells you to do. Good luck
Thanks
Dr.Par