But if you have doubts about whether or not you should eat something, you are sinning if you go ahead and do it. For you are not following your convictions. If you do anything you believe is not right, you are sinning.
But if you're not sure, if you notice that you are acting in ways inconsistent with what you believe - some days trying to impose your opinions on others, other days just trying to please them - then you know that you're out of line. If the way you live isn't consistent with what you believe, then it's wrong.