“Are lustful thoughts natural, and how do I deal with them when they keep coming back into my mind?”
God made the average young man to procreate. There are always exceptions to the average, of course, as the Lord Jesus noted to his disciples — that’s how it becomes an average in the first place. You need the outliers on both ends to put you smack bang in the middle of the pack.
You sound like you’re right there in the middle, Anonymous: a normal human, Christian male.