Rayray, it sounds like a phase. He says he isn't having a bad dream, but maybe he just isn't remembering it or able to articulate it properly? It could be anxiety with a new baby on the way. Not wanting all the lights on and sounding genuinely distressed, he is obviously looking for comfort from you. (My DD still naps for the same amount during the day and if this has only just started occurring I would doubt it was because of the nap).

Even if you can stop him turning on the lights, will that help him get back to sleep? What do you do when you put him to bed at night? Is it possible that you could somehow replicate this with him once he's woken (ie drink, toilet, cuddle, bed)?

He will grow out of it.