Hi M.,
I'm the mom of a 4, 2 and 7 month old. My first one slept through the night at 2 months and its gotten gradually worse with the 2nd and 3rd. However, my 3rd one has finally caught on to the household routine and is doing so much better.
Do rule out an ear infection, teething (which is very probable at 5 months) or any other health problem. If he is generally happy during the day, with a good disposition, then he's probably fine.
Here's my tips:
#1 You have to be diligent in your routine with both children, whatever you decide to do. You have to be strong and not give in. For sanity's sake. You will feel much more in control.
#2 Establish a routine with your baby. Here's my sample schedule. She wakes with the household generally around 7:30am.
I give her a bottle or maybe you nurse. About a 1/2 hour later, she gets breakfast - scramble eggs are a hit. She wants a nap around 9am. She sleeps til about 11.
She gets another bottle, then lunch - deli meat and cheese has been a hit. Her next nap is 1pm. You should aim to get both down from 1 - 3. Upon waking, she gets a bottle. Then a snack, then dinner. She eats what we eat - she loves hamburger and steak meat.
As long as she can mash it with her gums, she eats it and its what she seems to prefer. A bath if needed. She goes to bed at 7, rocking in her bedroom chair with the music (a que), then I put her in her crib with her paci and her blankie and I hit the button her crib aquarium. A soft square of fabric. She wakes between 12 - 3 for another feeding and then not til 7:30am. She did not do this til over 6 months. Remember, Sleep Begets Sleep.
#3 Establish "ques". A bath with soothing lotion afterwards, the music, the rocking, the blankie, the paci, the crib aquarium (Fisher Price). This has been a winner with all 3 kids. If your 2 yr. old, can watch a movie/tv or look at a book, while you do this, that would be great. However, I know this is not always the case. But keep going with the routine, let the 2 yr. old get mad, if it has to be.
Then, you should follow suit with his bedtime routine. Aim to have everyone in bed by 8pm.
#3 HAve him eat throughout the day. Keep him active - go to the park, play in your yard, take a stroller walk, throw him in the air, etc.
#4 At 6 months, you can let him cry it out, if you choose. Turn the monitor down, take a tylenol PM and get your rest.
YOU are the most important person in their lives and they need you at your best.
#5 Reiterating, you need to stick to a plan of action. You will feel so proud of yourself. Don't expect it to be better until after 6 months, but start now.
M., I feel for you, because I do not get a lot of sleep. There's always somebody up or my other two awake at 6am, when I had finally fallen into bed at 11pm doing housework, bills, email, etc.
Try to remember the blessing of having happy, healthy, children.
Write back in you want :) Good luck,
L.
P.S. Remember to give a sippy cup with water all day. I noticed that my baby is parched most of the time, especially formula makes them thirsty. I've left a sippy cup, the one with handles in her crib, thinking eventually she'll pick it up and take a sip.