*Should I fight custody?*already signed sep.agr

[cat03]

compared to what others are going my whine is somewhat petty, but I have to vent somewhere!
Despite telling stbx that his gf is not to set foot in my house, he's yet again let it happened! he was late and she was the one who brought the kids clothes and the dog. He's a little bichon who is an indoor door, stbx used to have a key and would drop dog/clothes before he had to go to work. Since he as no key now we have a problem, once i picked dog up (gf was there, son picked dog/stuff up) and a few times stbx picked dog up from my enclosed back porch.
Today he had to go in early and she was the one who dropped the dog and clothes on my back porch. It was freezing and there was no food for the dog, it is an enclosed porched but it is not heated and it can be very cold there, I was so mad when after txting stbx I learned the poor dog was there all day with no food.
The freaking liar told me he dropped him off before work, I learned by my s10 that it was gf who dropped dog off in the morning. ARGHHHH!! why does he have to LIE so much?? I know I shouldnt' expect any better, but it just made me so mad, he is such a looser, grrrrrr @#$@#%$#%$#% I called & he didnt' picked up, just left an vm telling him to not leave the dog on the cold and to tell me if he is unable to drop the dog off, I was so po'd.

ok...ok... ranting over... bleah, I hate it that I'll have to deal with him for years to come...