Hi Jess, sounds like he is jealous to me. The very fact that your daughter is so young would probably make any man worried that she will grow up thinking of your boyfriend as her daddy and not him. This isn't your fault at all, but I can understand you're stuck inbetween a rock and a hard place. The fighting is not good, at all, and perhaps when your ex is coming to get your daughter you could just ask your boyfriend to keep out of the way until he's gone, I know that sounds unfair on him, but one of them has to be the bigger man here, and your ex doesn't sound like he's going to be it. If he takes you for joint custody then the fighting is going to come up, and no Judge is going to like that. I really feel for you, and I don't know what else to suggest, I can imagine it's putting you in a very stressful situation. Your ex sounds pretty angry and jealous - maybe even of your boyfriend's relationship with you, you never know - and until you come up with a more permanent answer it's best jsut to keep them separate before they end up seriously injuring each other!!
Hope this helps, even a little!
Tc