D.T.
My daughter has the worst emotional extremes, and can't seem to self soothe at all (she too is newly 5). So I completely understand. There are some things I've found help... and will feels things are going really well. Then we have a rough patch. They are getting shorter and fewer though. So I think we are on the right track. First, I really had to clamp down on her. I felt bad... but I learned if I stop it before it escalates, then it just doesn't. So once the fit starts, she is sent to her room or time out. That simple. You'll have to pick a consistent pattern and stick to it. Like everytime she fights me on something she is in time out. If she can't settle down after time out, but isn't fighting me anymore (the crying and wailing in upset) then she is in her bedroom for some "alone" time or "cool-off" time. She'll be in there until it stops. Sometimes its 10 minutes, sometimes an hour. But either way, she has to learn how to handle her emotions, and it also gets her away from whatever started it. It took a bit for her to figure out we weren't going to come and get her when she was screaming. And man did she scream! But it really is getting better now. I also have a no tolerance rule when it comes to throwing or slamming doors. Without any words, if something is thrown in her room, I go in and take it away. She has to earn it back. The doors, well, I give them one warning and the next time I take if off! She does NOT want that door off so that works great!
With tv, video or computer games I made something that worked like magic. Really. I bought the colord popsicle crafting sticks and assigned each kid a color (right now i have two I do this with). I wrote their name on the sticks so there is no "forgetting". Each stick has a time written on the end. Ours say 30 minutes. You can decide how many they get per day/week. I give them say 2 a day, and then one or two movie sticks (which are a new color neither of the kids have) which are for the week. So once they use their time, they can no longer watch or play. They can use that 30 minutes for tv, or computer or whatever... but when they are gone they are gone. And I have the kids move the stick out of the bucket, so they can see they are "spending" their time. It works so well! And if both are watching the same program on tv, they are both using their own time. It was really empowering for them to get to choose what they do with their time. You could assign time to different media (tv vs. computer) but mine seemed to like the learning games on the computer better anyway, so I just left it with whatever. You could decide on that! Oh, and I have 10 minutes sticks they can earn for good behavior. I never brib with earning one.. it ends up working against me when I bribe, but just knowing they can get one helps a lot!
Staying in bed is tough. Do you have a night light? That might help. And unless she is really scared, go in and give her a quick love. Tell her you love her and you are going back to bed. Then ignore her. It may take hours for the first bit... but she'll get it. Really she will.
I hope any of this helps. I really feel for you, because we are there too! If you have want any advice with anything in particular let me know.... it may have been something we were able to find a solution to! Or, if you just need to vent I'm here! I too am hoping this is something she outgrows. Ugh!