Well, first of all the remorse you are showing is much different than an unsaved person would likely show. For the lost, there really isn't any true desire to stop living a sinful lifestyle until it causes problems. Up until then, they're perfectly content getting away with things.
However, I may be wrong, but it sounds like the sins you've done were mostly done in secret and you are feeling extremely guilty and distant from God as a result.
I've been there. And still am there sometimes. Not too long ago, I sinned so blatantly that I actually felt sick to the stomach afterwards and questioned my salvation again, just like you are doing. Yet, I truly believe I am saved and do have assurance of my salvation. Personally, I see these things as Satan's way to get us to give up hope and stop pursuing God. When I sin so greatly, I figure that God is about to do something great through me perhaps, and Satan is desperate to make me stumble and prevent it from happening. So hold on.
The passage I often return to for comfort after feeling like there's no way God could ever forgive me is Isaiah 57:14-21.
14 And it will be said,
“Build up, build up, prepare the way,
Remove
every obstacle out of the way of My people.”
15 For thus says the high and exalted One
Who lives forever, whose name is Holy,
“I dwell
on a high and holy place,
And
also with the contrite and lowly of spirit
In order to revive the spirit of the lowly
And to revive the heart of the contrite.
16 “For I will not contend forever,
Nor will I always be angry;
For the spirit would grow faint before Me,
And the breath
of those whom I have made.
17 “Because of the iniquity of his unjust gain I was angry and struck him;
I hid
My face and was angry,
And he went on turning away, in the way of his heart.
18 “I have seen his ways, but I will heal him;
I will lead him and restore comfort to him and to his mourners,
19 Creating the praise of the lips.
Peace, peace to him who is far and to him who is near,”
Says the Lord, “and I will heal him.”
20 But the wicked are like the tossing sea,
For it cannot be quiet,
And its waters toss up refuse and mud.
21 “There is no peace,” says my God, “for the wicked.”
Keep in mind the story of Hosea. It's an analogy of God's relationship with wayward Israel, but can be applied to us, too. Gomer doesn't simply leave her husband, she literally sells herself as a slave to sin. But, against all logic, Hosea buys her back. That's the love of God. Even when we've sold ourselves to sin, He still has a claim on us and won't rest until we're with Him again.
And then there's the prodigal son, and lost coin and lost sheep parables that you probably know. People assume these are all about unbelievers, but in reality the prodigal son was already a son before he wandered. The sheep was already in the fold before it wandered. and the silver coin was already part of a headdress before it came off and rolled away... something to keep in mind.
Blaspheming the Holy Spirit does not mean you can sin to the point that you can never return to God. Blaspheming the Holy Spirit has to do with attributing His works to Satan, which no one would likely do unless he wasn't saved to begin with.
Also, when it feels like the Holy Spirit has left you, go to Psalm 56. It struck me one day how strange and powerful the title of this psalm is. I'm sure there's an explanation, but regarding the fact that the Holy Spirit is often likened to a dove, the title "A Silent Dove Far Away" is captivating. The psalm goes on to ask God for protection from enemies and expressing trust that the Lord is on our side and will do exactly that. David expresses the truths that God sees us wherever we are and knows all our griefs and that He's on our side. But in the moment of despair, God (the Holy Spirit) can seem like just a silent dove far away... Like He's not even there.
Finally, not to promote myself at all, but I have written plenty of songs based on experiences very much like your own. Perhaps you'd find this particular one comforting:
My Ally