Sleeping

My little one was born 4 weeks early and since he was born he was amazing sleeper. He would always sleep which was great because none of my kids never slept. I thought great last child and he's amazing but i was so wrong he turn 5 months last month and my god he just don't sleep he wakes up every 2 hours in the night and naps every 20 minutes during the day.

During the day i look out of the signs of tiredness and get him ready for a nap but as soon he's asleep, doesn't matter how long he will wake up and won't go back to sleep.

During the night he use to sleep 8-10 hours now it more like 2 hours, it doesn't matter what time he goes to bed he always wake up excatly 2 hours later, i got to go into the room and rock him back to sleep. He can drink 7oz in formula every 4 hours and that's including the night.

He sleeps in our room with his sister so he always wake her up i can't put him in his own room as we got no other room.

I have change his next to me crib to a cot bed so he have more room but nothing.

I know he's teething.

He can't have solids yet because he still can't hold his body up.

I have tried books, internet, the cara sleeping scheme but nothing works.

The thing is he doesn't sleep but still a happy baby.

I have no idea what I'm asking i have tried everything i don't know whats left I'm just so tired, cranky, miserable, I'm sitting here watching bing with my two little ones qnd if i do fall asleep my toddler thinks it funny to pull my eye lid open 🙈

Sorry if it don't make sense and missing words/letters i have been up for ages. He turns 6 months on Wednesday.

Thought i would mention his dad is always away with work so its just me. When he is back he does hes bit/bathing, playing, etc and cooks me a nice meal because i just don't have a chance to eat. properly.