I Thought Rejecting The Lord Jesus Christ Was The Unforgivable Sin

You have it backward.  The unforgivable sin (as described in How To Tell If You Have Committed An Unforgivable Sin) is rejecting the Lord Jesus Christ.  For example, Titus 1:16 says, “They profess that they know God; but in works they deny him….”  As regards the Lord Jesus Christ, since the Lord Jesus Christ is God, this means “They profess that they know…[the Lord Jesus Christ], but in works they deny [reject] him.”

In other words, every unforgivable sin is a rejection of the Lord Jesus Christ.  To explain further, one does not have to say “I reject the Lord Jesus Christ” to reject the Lord Jesus Christ.  One might reject the Lord Jesus Christ by refusing to feed the starving or by failing to aid the sick or by cheating on one’s spouse.