It's not that easy.
I didn't see my abusive relationship as abuse because he spent a couple of years grooming me to lower my standards, which weren't high anyway due to my abusive childhood.
Then you don't think it's abuse because he only pushed you and it was your fault.
Next it was just a slap, and you can't really say anything because you deserved him pushing you, and did something worse this time. And on and on it goes.
But it's not like that all the time. In between times, there is happiness too.
It's easy to look back, or look from the outside and realise the abuse. It's not so easy to see things when you're in the midst of it.
There's also the fact that if you leave your child/ren will have unsupervised contact. At least if you're there he's taking it out on you, what happens when you're not there.
Also you say women's aid - which I used, but it takes a long time, they can't always help immediatly.
Abuse is so complex, its not about being desperate for a relationship ffs.