I have a two year gap between eldest two. 3yr old and nearly 1yr old is pretty much the hardest time ime.
Toddler wanting your attention, baby too young for them to play with properly. Baby not sleeping, needing your attention, still needing breast or bottle, weaning taking energy, shitty nappies, baby wanting to copy toddler but not able to because not walking, still needing a pram everywhere, everything is just EFFORT.
I remember it so well.
This is the worst bit op, you're nearly at the turning point so just try and buckle down and hang on. People saying it doesn't get easier are chatting nonsense. It will get SO much easier, soon.
When you have a 2 and 4 year old they'll hopefully both be sleeping through. Both just eating normal family meals. They'll play together. No more pram, no more weaning. End of nappy changing in sight. Eldest in school. Take them to a secure park and they'll both wander off to play.
Another year after that you can send them off upstairs together to play for half an hour whilst you sit with a coffee. Then before you know it they'll both be in full time school.
It might not feel like it but you're nearly there and you won't recognise yourself this time next year.