Hmmm...
Well, if you are, then most of us are guilty of that one!
Actually, I really don't know the answer. I would never tell someone that I know for a fact that they are sinning, because only God can truly determine what is in your heart and your mind. However, I know that we are to devote ourselves to what is good and pure and right - and I
would venture to say that there are a lot of better things that you could be doing with your time. Often I judge myself this way - if I
question whether I am sinning or not, my heart is probably not in the right place and I try not to do whatever it is that makes me feel as though I am questioning my morals in the first place. Basically, better safe than sorry.
Romance novels are, just in my opinion, a total waste of time. Not one plot line ever seems to make any kind of sense, and you really gain no knowledge or insight from them. Wasting your time, in a way, could be considered a sin, when there are better things you could be doing. Of course, there are much better things that
I could do than sit around and watch Maury Povich, so I am definitely not trying to judge you!

But when you question yourself, it's usually a sign that something's not right. Be proud of yourself for recognizing that, but the next step is, how do I improve myself now that I have recognized it?
That all said, sex is a beautiful thing, one that creates life and makes people feel blissful, and also one that's written about in the Bible. It's all about context. Next time, I suggest you put down the Harlequin and check out Song of Solomon. Talk about sensuality!