Yes I left my XH, we had 2 children and we were married for 10years. Just like you, it was the 'make up and break up' gift that kept on giving.
The fact you call yourself weak and pathetic (you aren't, by the way) makes me wonder if you are getting back with him out of routine and a falsely-held duty, rather than love. It was that for me. Or because the idea of going it alone is intimidating, after so long.
That happened with me, but eventually you realise that it chips away at who you are, and staying 'for the kids' rarely works, even less so if you are on and off! It must be as confusing for them as it is tiring for you
We'd spent the last Year of the marriage totally without closeness or intimacy, he'd hurt me that much I couldn't stand him to touch me- but was still sticking with him for the DCS and because of the comfort in familiarity, but I wasn't happy. In fact I was desperately unhappy but had no-one to admit it to.
I went on an evening out with friends, and an absolutely beautiful man started talking to me. I was honest, said I was married, and left after a conversation. Nothing happened but I wanted it to. It helped me and my confidence no end, that a man would still find me worthy of a conversation, and found me attractive. Something woke up in me that thought, "i actually do want to be seen for more than just a cleaner, arse-wiper and part of the furniture- i wanted to kiss, hold someone and make love have great sex but just not with the man I married. It had gone.
We had nothing holding us together anymore except the children, being raised in a home where their father was unreliable and immature, and their Mother wasn't happy.
You just have to be ready to make the break, and be strong enough to keep your resolve. 