NO - temptation does not equal sinful lust. Even Jesus was tempted - and "in every way, just as we are--yet he did not sin" (Hebrews 4:15).
It is our RESPONSE to temptation that can be sinful lust. All manner of things and situations present themselves - things that we don't necessarily seek out - that pose temptation to us, that lead to sin.
In this discussion, while I do see merit in understanding ourselves, our histories, and our triggers to whatever sin - be it porn or anything else, I also see a huge post-modernist compulsion that is complete psychobabble, that makes us think we have to comprehensively understand the intricate dynamics of our behavior in response to our temptations, or how our we might dissect the minutia of what part is sin, what isn't, where one begins and the other ends, and to accurately parse all of our complex motivations and causes. The reality is, God has shown and instructed us as to what sin is. Craving and desiring something that is not rightfully ours and that is forbidden to us is sin. Period! And any Christian (and only a Christian) who has experienced and/or studied the horrific impact of porn and it's long legacy of horrific devastation to marriages and families, who also has studied Scripture to understand it is a sin that is highly addictive, deceptive, and a very difficult habit to break, should realize they already know ALL they need to. We don't need to perfectly understand ourselves, our motivations and triggers - while all those can certainly be beneficial - ultimately, we simply need to FLEE the temptation and sin - and at first awareness of it. And for all aspects we feel it might be useful or fulfilling - which are lies we buy into - we should instead turn to God to take away desires not healthy for us, and to fulfill us in HIS ways, to spiritually fill us and our true needs, as opposed to our dependency upon things we might seek out that are sinful, that we often convince ourselves we need. And, if we're not careful, if we don't allow God to do the fulfilling of the desires of our hearts and minds, we'll simply go from one sin to other ones, or back again, seeking to fill our voids that only God can truly fill.