You have probably already heard this before, but I just thought I'd add my two cents in case it is of any help. I have an 18 month old and I too was spoiled by him sleeping through the night at 8 weeks, only to find that it was temporary. Then we moved when he was 4 months old and that's when he stopped napping AND sleeping through the night. I think they can sense when there are changes and tension and it affects them similarly to how it affects us.
What I found to be the best solution was letting my son cry it out. It was very difficult at first, but it got better and he turned into the best little napper there ever was and has slept consistently through the night (11 hours!) since 11 months. I would make sure he was well fed and had a clean diaper before bed, would offer him a bottle, which he rarely passed up, then followed a routine of teeth-brushing, bed time story, lights out, night light on, music box on, kiss goodnight, and then I'd leave the room. We still follow the same routine 7 months later and now he doesn't even bat an eyelash at bedtime.
My son is a strong-willed boy and it took a while to get to this point but it was worth it, he knows how to soothe himself back to sleep. If/when he wakes in the night (he used to wake much more than he does now) I knew he wasn't hungry because he had been well-fed before bed and then had a bottle, so I would let him cry until he fell back asleep. Once he realized that his crying wasn't going to work he would go back to sleep and eventually if he woke in the night he would just talk to himself or kick the button on his music box to turn it on (its one that attaches to the crib) and would fall back asleep without making a peep.
Also, I found that making his bed time a bit earlier actually helped! I know it sounds strange and it may not work for you, but he actually slept better and longer the earlier we put him to bed. We started small, moving from 8:30 to 8:00, then 7:30, then 7:00 which was a great bed time for him. (Now he goes down at 7:30 since he doesn't need quite as much sleep as before.) Eventually you will get used to his routine too and will know if he's waking in the night because he just wants to play or be held or if he really needs something. My son rarely cries in the night now, maybe once a week, and its only when he has a poopy diaper. So I will change him, follow a shortened version of his bedtime routine, night light on, music on, goodnight kiss, then I leave. It seems to work really well for us, but it did take some work. I think anyone can do it, you just have to have patience and perseverance. Take heart, sleep is near. Good luck!