John writes, "μονογενής", which means:
"
only...Also
unique (
in kind) of someth. that it the only example of its category...'
unique and alone'" (W F Ardnt and F W Gingrich; A Greek-English Lexicon, p.529)
"
the only member of am kin or kind: hence, generally,
only, single, unique" (H G Liddell and R Scott; A Greek-English Lexicon, p.1144. Revised Edition)
"μονογενὴς is literally “one of a kind,” “only,” “
unique” (
unicus), not “only-begotten,” which would be μονογέννητος, (
unigenitus), and is common in the LXX in this sense" (J H Moulton & G Milligan; Vocabulary of the Greek New Testament. pp. 416-417)
“But the word can also be used more generally without ref. to derivation in the sense of “
unique,” “
unparalleled,” “
incomparable,”” (Gerhard Kittel; Theological Dictionary of the New Testament)
IF John wished to say "only begotten", then he would have used the correct Greek word, "μονογέννητος"
You are trying to force your theology, as some others do on here, into what the Bible actually teaches.
You will also notice, that the original NASB reads "only", and not "only begotten"
Bible Gateway passage: John 1 - New American Standard Bible