My son is nearly 3.5 , and my other son is 6.5 months. My first sons behaviour did change when I first gave birth, just the normal I think; regression in potty training, being a bit rough with brother, becoming naughtier, more attention seeking. But on the whole he seems to love his brother, and likes to help etc. He also started a new nursery in January, so I realise a lot of change for him. He has also suffered 3 throat infections from November- Feb 2019 (which may have more relevance). When he started nursery he was very very challenging at home straight after being picked up , chatted to the teacher, they said he's doing good, and alot of parents say this and could be due to tiredness, but it should settle down. He has got better but still naughty. I know all children are naughty, and he had his moments previously, but some days he will just do naughty things continuously! He is not himself it seems! I don't know if he is acting out because of his brother, or if it's the nursery. I should mention he does go straight into nursery no problem, and seems to be happy, but I do know there is quite a few boisterous characters in the nursery, so I think he could be copying the behaviour. I'm staring to doubt myself now aswell, I'm pretty tired with baby, and maybe I have changed too. I just don't know 
. He has also now stated doing this eye roll/blinking thing, which I first noticed before he started that nursery for a few days because he was tired i think, but now he's been doing this a few days, I thought dry eyes and he has drops but I'm wondering is it a tic. I don't know but I just feel there's something not right, but I also know I'm very anxious and a worrier! I've been googling different things (which probably shouldn't) but I've seen something called PANDAS which can be brought on from strep infections and cause behavioural changes. Or there's also sleep apnea ? The doctors said he had quite large tonsils, and he might snore, and I've read this can cause sleep apnea, which may be why he is tired, and why the tic has gone back! I don't know what to do I've already viewed another nursery, which is lovely, but I don't want to jump to conclusions and take him out if it's something else . I dont know what to do I feel tired and useless , help !!!!!