Trump wants to win. He has never held back his feelings, and people are so surprised at this that they believe he must be pretending to want to win. If he did not want to be president then he would have backed out by now. No one knows what to expect from Trump in his statements. It doesn't mean he wants to lose.
I don't think Trump spent so much time, money and energy campaigning just so he could lose. He's a businessman after all and I don't think he does anything to lose. Plus, this is the race for being the President of the United States, there is no way he would intentionally give up such a powerful post.
I don't believe at all that Trump is trying to lose the election. His decisions are unconventional at times, but he doesn't accept failure in any area of his life. IF anyone is trying to lose, it would be Hillary, since she is running after her dismal performance and suspicion regarding her time as Secretary of State.
Donald Trump's ego is too big for him to want to lose. He may have gotten into the election as a bit of a joke, a chance to make noise, but now that he's the Republican party nominee, he wants to win it. I do think the whole thing went further than he ever expected, but he had the option to withdraw at any time, if he really wanted to.