Was the virgin birth and resurrection of Jesus Christ a myth?
There’s a problem with the details of jesus’ life. That problem is that other than the bible, which is clearly biased and contains many unsubstantiated claims, such as the virgin birth, which really should require further proof before accepting them as true, there are no other sources anyone has for those details. You are however correct in saying that the virgin birth idea was quite common in religious teachings in that area at that time. This is quite likely where the jews came up with the notion (if you accept the translation of “young woman” as “virgin” anyway), and then the details of jesus’s birth are clearly made to match the prophecy. If you doubt the truth of the bible, as you should considering accepting based on blind faith is not usually the means to establishing truth, then you can establish very little about jesus, and certainly nothing about the sexual experience of his mother prior to his birth.