Yes, “unforgivable sin” is the same as “everlasting sin.” Both are describing the “sin against Holy Spirit.” Both are sinning while having accurate knowledge; knowing that you are fighting against the work of the Holy Spirit. They are not due to ignorance. This can be seen by examining the parallel scriptures and their contexts.
Mk 3:28-29 contrasts sins which “will be forgiven”and “blaspheming the holy spirit” which “has no forgiveness forever” (i.e.; unforgivable) which makes them “guilty of everlasting sin.”
Gill’s Expositor says: “...guilty of an eternal sin; a sin which can never be blotted out, and will never be forgiven, but will be punished with everlasting destruction”
Mt 12:31-32 is the parallel and makes this clear: “Every sort of sin and blasphemy will be forgiven men, but the blasphemy against the spirit will not be forgiven....whoever speaks against the holy spirit, it will not be forgiven him, no, not in this system of things nor in that to come.”
You noted Heb 10:26 which highlights that “practicing sin willfully after having received the accurate knowledge” means “there is no longer any sacrifice for sins left, 27 but [there is] a certain fearful expectation of judgment” and again in verse 29 to show that this is the sin which “has outraged the spirit of undeserved kindness.”
Heb 6:4-6 is also shows this is a sin committed by “those who have once for all been enlightened...and who have become partakers of holy spirit.” It is impossible “to revive them again to repentance.”
Here are a couple of pertinent references:
*** it-2 p. 969 Sin, I ***
Jesus told Pharisees of his day that if they were blind, they would have no sin, evidently meaning that their sins could be forgiven by God on the basis of their ignorance; however, because they denied being in ignorance, ‘their sin remained.’ (Joh 9:39-41) Jesus said they had “no excuse for their sin” because they were witnesses of the powerful words and works proceeding from him as the result of God’s spirit on him. (Joh 15:22-24; Lu 4:18) Those who, either in word or by their course of action, willfully and knowingly blasphemed God’s spirit thus manifested would be “guilty of everlasting sin,” with no forgiveness possible. (Mt 12:31, 32; Mr 3:28-30; compare Joh 15:26; 16:7, 8.) This could be the case with some who came to be Christians and then deliberately turned from God’s pure worship. Hebrews 10:26, 27 states that “if we practice sin willfully after having received the accurate knowledge of the truth, there is no longer any sacrifice for sins left, but there is a certain fearful expectation of judgment and there is a fiery jealousy that is going to consume those in opposition.”
*** w82 4/1 pp. 27-28 par. 7 Survival or Destruction at the “Great Tribulation” ***
The very fact that Jesus stated that “blasphemy against the spirit” would be forgiven neither “in this system of things nor in that to come” should convince any who have doubts on the subject that Jehovah pronounces final judgment against some even during “this system.” Such become “guilty of everlasting sin.” They will have “no forgiveness forever.” (Mark 3:28, 29)
Now with the additional comments I see that we have been answering your question intellectually when you really also needed an answer to address your emotional questioning. Sis, all of us who have at one time or the other sinned grievously have wondered if we had committed the unforgivable sin since we had knowledge of right and wrong. But, the very fact that a person feels bad and wants to--or has corrected their error proves that they have NOT committed an unforgivable sin! The fact that a person desires to continue fighting against wrong practices proves they can still come under the ransom arrangement!
It is exceptionally hard to sin against the Holy Spirit and requires an open and purposeful rebellion against God and His representatives.
”By this we shall know that we originate with the truth, and we shall assure our hearts before him 20 as regards whatever our hearts may condemn us in, because God is greater than our hearts and knows all things” (1Jn 3:19-22).
(Jas 5:14-16) Is there anyone sick among YOU? Let him call the older men of the congregation to [him]...And the prayer of faith will make the indisposed one well, and Jehovah will raise him up. Also, if he has committed sins, it will be forgiven him.
(1Jn 2:1-3; Rm 8:34).