Ugh why did i do this?

My partner if 7 years and I split in April. We own a house together, which we are currently trying to sell.

Right after we broke up, he tore his arm tendon and had surgery, so was staying at his moms vacant apartment while I got everything fixed up to list.

Anyhoo, I have trained on a new system at work, so HAD to go to the office to learn it, while he's been here with the kids.

So, last night he was here. I helped his friend get some bunk beds back to his new place, and then went home.

I was in a great mood, and he was kinda looking good. Despite me keeping boundaries thus far (he has been seriously regretting his life choices) he has been tyring to get hugs, etc. I blow him off every time. Tell him I can only offer him a friendly throat punch.

However, last night one thing lead to another and we ended up having mind blowing sex.

I can't ever be with him again. I know that. He knows that, but he's back to the I love you, and I miss you stuff.

What he did was fucked up (not cheating). We have 1 bio child, and my twins call him daddy.

It is easy to fall back into old ways after 7 years together, but I know it's not a matter of if he will pull this shit again, it is a matter of when and I'm not here for that.

I've tried to reestablish the boundaries again, but I haven't seen him since this am. He is coming back tonight and staying until Thursday.

I feel like I've gone backwards and I honestly have been looking forward to a new home and new beginnings.