Weird. I wrote a long response to this and it somehow disappeared.
My answer was: Do whatever you feel like doing at the time. This could be singing loudly or screaming (that's what helped me, not only with the pain, but also with focusing my energy and allowing myself to open up), walking, dancing, sitting, bouncing on a body ball, going outside, breathing, whatever it is that you feel like doing- give yourself permission to be as weird as you need to be. Trust your body and your instincts. You were built for this!!
I also want to echo what someone said below about trying to escape from or ignore the pain. I also think that can contribute to your fear... and repressed fear keeps people from dilating. The thing to remember is that in normal life pain means that something is wrong with your body... but in childbirth it's just part of the process. The pain is just there, it doesn't mean that something is wrong. If you trust your midwife or doctor, then you don't need to worry that something is wrong... leave that up to them to pay attention to. That's what they're there for.
It's gonna hurt. You know that. From what you say, your fear is about whether you can do it or not. I'll share with you the simple realization that I had when I was working on facing that fear myself: You don't have a choice about that anymore. It's too late. That baby is coming out no matter what you do. You have no choice but to go through the pain until it's over with. If you get to a place where you feel like you're going to lose it... go ahead and lose it. It won't last forever. You will go through it and find yourself on the other side of it feeling very empowered and holding your amazing and wonderful new baby in your arms. :)
You can do it!! This is what your body was built for!!!
PS. I just want to say also that I'm sorry for your loss of your second baby. I lost a baby at 13 weeks (my first pregnancy) and not only did it take me months to heal emotionally from that loss, it also affected me psychologically and emotionally during my next pregnancy (a healthy boy- born 9/27/09!). It can be a challenge to work through that kind of a loss. I hope you are able to honor that during your current pregnancy... and that you have support to talk it all through.