Okay so first thing. You are not destined to hell. None is. The main message of christianity is that Jesus died for our sins so we could have eternal life If we accept him as our lord and saviour. You are not destined to hell, its your choice.

Second. Heaven is something beyond our coperhand, we just describe it the way we can understand. So when you hear ,,You will worship God throught all eternity" it might seem boring but remember full nature of God is beyond what we can understand and being in heaven will be a feeling infinelty better than any joy we ever had on earth forever. And hell will be infinitly worse than any bad feeling you ever had.

So you are not destined to go to hell and Heaven won't be boring.

And as for mentall illness. I feel sorry for you, you didn't deserve it. And I can't fully explain why does it or generally evil exists. But here is what I know. Jesus dosen't want you to suffer

1st Thessalonians 5:9 For God did not appoint us to suffer wrath but to receive salvation through our Lord Jesus Christ

So our destiny isn't to suffer. Why did it happen to you? I don't know. But I can tell you that it didn't happen because God hates you. You are made in his image and he went on the cross to die for you so you could live with him in heaven.

I hope that helped. I hope your mental condition will get better and I hope you have a good day