For this topic, I have armed myself with chocolate as I type. I wonder if that's a sin?
Broadly speaking, there are two Christian schools of thought on sin.
One divides sin into two kinds: mortal sin and venial sin. This kind of approach has its basis in the kinds of things said in 1 John 5: "If you see your brother or sister committing what is not a mortal sin, you will ask, and God will give life to such a one—to those whose sin is not mortal. There is sin that is mortal; I do not say that you should pray about that. All wrongdoing is sin, but there is sin that is not mortal." So this kind of approach draws a distinction between "petty" sin, if you like, and the really serious stuff.
The other points out that all sin is of essentially the same kind. The difference between so-called mortal and venial sin is not one of kind but only of degree. This is the way that Paul tends to write about sin in many of his letters, but an example would be when he says that "the wages of sin is death." He doesn't make a distinction there; and he's right insofar as all sin is a falling short of the glory of God; all sin is a failure to be the person I am created to be; all sin is a participation in the sickness, the slavery, the death which has humanity by the throat.
As you can see, there's a Biblical basis for both ways of thinking about things. I think both of them say important things about the human reality of sin; because I, too, don't think God sees all wrongdoing in exactly the same way, even if it is all "wrongdoing."
I also think that there's a question of context. It can be argued that what John was talking about in his letter is the sin that believers commit
after conversion, after baptism. Post-baptismal sin was a huge issue in the early church; many believed that if you committed a mortal sin after your baptism you betrayed God and irrevocably forfeited your salvation (which is one reason why some people delayed baptism even until their deathbeds, for fear of sinning too badly afterwards).
Whereas it can be argued that Paul is talking about the reality of sin
before conversion; when he talks about the wages of sin as death, he does so in the context of presenting faith in Christ as the life-giving alternative. He is putting a choice in front of his readers: choose the sinful system of this world (and therefore death), or Christ (and therefore life). In that context he doesn't need to make a distinction between murder and excessive chocolate consumption, because without Christ (in his view) there is no escape from death at all.
Doomed to hell? After much wrestling with this, I have come to the personal position that I believe that those who don't go on to eternal life with God don't go to a place of eternal torment, but have their existence end after this life. I guess I don't believe in a stereotypical cartoon hell. But that's really a whole separate topic!