It gets better. You are probably right about the nursery, but be aware that also, they just go through mad little phases where everything is off kilter and it's nothing you've (a) done or (b) can 'cure'.
My DC2 is 5mo and has been doing 'normal' nights but randomly tonight has been awake til about 10 minutes ago. Who knows why? I have no idea. The sleep disturbance does cause you to feel like shit, but honest to god, it's so, so fleeting that they are so small, you will manage and he will get over it.
My only 'tips' would be to keep doing what you do at night to put him to bed, don't panic if he doesn't settle, go to bed mega early a couple of nights a week (at the same time as him!), don't spend your evenings 'trying' to put him to sleep. I put DD to bed about 8; she didn't settle, so I gave up and got her up. Put her in a wrap because I had to pop out, made myself some food, now she's crashed out on my lap and I am happily MNetting and watching The Great Australian Bake Off on Youtube. We co-sleep so I'll just take her to bed when I go; if she was in a cot, I'd settle her before knocking off to bed myself. If she was in a cot, and wouldn't settle, I'd sneak her into my bed for the evening just until she was through whatever phase it is that means she didn't want to go to bed alone. Don't worry about forming habits - if they don't suit you, you can form new ones just as easily.
I know that everyone says it and I've even said it myself already - but this will be over in the blink of an eye. Don't sweat it, it's totally normal and it's not because there is something wrong with the baby or something wrong with what you are doing. Find a way to survive this phase - Australian Bake off is part of my own strategy -and be kind to yourself in the mean time. We have a rampaging toddler who is happy to go bed, sleeps though, even sleeps through the baby waking! And he was no different the baby at this age, but I do remember worrying endlessly about what I should be 'doing'. The answer is always, always, 'as little as possible;' whatever it is will most likely settle of its own accord as long as you stay steady.