Lack of sleep

Our toddler is almost 3, he still usually doesn’t sleep through the night. And now he just opens his door and climbs into our bed. Which I don’t mind. But it usually wakes up our 7 month old. Who then is up and chatting and ready to eat. Then they’re both up at 5am. I haven’t had a full nights sleep in 3 years. I’m exhausted. My husband works 6 days a week (I work 5 days a week) and he’s a very heavy sleeper so he hasn’t don’t any night feeds or wake ups since our littlest was a few weeks old. How are you guys coping with the exhaustion? I don’t want to lose my temper or not be present with my kids, but I’m running on fumes here.