I don't think he would hit me. He doesn't like physical abuse as he was physically abused as a child. And I know how he would react if I tried leaving the room while he was screaming at me. He would either stop me by physically restraining me or would say things to me that would make me not leave, like threatening to end the relationship.
You really need to set some boundaries.
What do you mean by physically restrain you? Does he grab you by the arm or does he block your way? That is NOT okay.
If he is threatening to end the relationships if you walk out, that is purely a manipulation tactic. This is a hard question to ponder. Do you feel like your relationship is more valuable than your mental and physical safety? Screaming at you and physically restraining you IS abusive. My husband used to make threats and innuendos about suicide. He used to also talk about ending the relationship. I got him to stop the suicide talk when I told him that if did it one more time, I was going to call the police and have him committed because I wasn't going to stand by and listen to that. When he would try to manipulate me with threatening to end the relationship, I told him to go ahead and started talking about what it would take to make it happen. When you do set boundaries and call their bluff and insist that he treat you better, it might even get worse for a while. That is why it is so important to equip yourself with as much knowledge about BPD as you can. And, make sure you read all about the different communication techniques.
And when ever I try to explain what I meant or what I ACTUALLY said, he tells me how impossible I am to talk to.
You trying to explain yourself is known as JADEing. You can read about JADE in the communication stuff on this site. JADE stands for justify, argue, defend, explain. I used to do it all of the time. I thought that if I just explained it a little better, he would understand. If I defended myself or justified myself just so, then he might get it. The truth is that he isn't going to get it and all you are doing when you try to explain yourself is adding fuel to the fire. There is a good chance that he is going to get mad no matter what you say. It is better to validate whatever it is he is feeling that is valid and not say much else. I still struggle with that. When you JADE, it is giving them more words to twist and contort and blow out of proportion.
Lately he has been talking to some women online who is from new zeeland. He talks to her about what is going on between is and it kind of pisses me off. I try to tell him how I feel, but he thinks I haut don't want him to have friends. That's not the case, this women has no idea who he is, they've never met. She only knows what he tells her. And he locked the computer so I can't see what they talk about. Which of course I don't like either. Promiscuity is a trait that he has shown before, I know she's far away, but I feel as tho he's having an emotional affair which he thinks is ridiculous.
You have every right to be angry no matter what he says. My husband and I experimented with an open relationship for a while and he would get online and talk to all of these women. I got into his stuff and found out that he was telling some woman horrible things about me that did not resemble anything close to reality. The thing is that he is going to deny that he is having an emotional affair. He is going to deny that he is doing anything wrong. My husband used to get mad at me when I would question him about his pornography use. He had progressed to preferring porn and self pleasure over being with me. I was dismissed completely. There have been lots of times when I have had concerns about things only to be dismissed. My husband has finally (after 16 years) admitted to being a sex addict and is in a 12 step program. What you are describing is very common for people with BPD and addictions. It is their way of protecting themselves.