I am not a doctor, but it sounds like you are one of us "unusual"/atypical girls. Or possibly you started your pregnancy with some underlying conditions like maybe kidney issues that you've never known about that are showing up now.
I went into the hospital with severe upper right quadrant pain. My blood pressure was normal and I was not spilling any protein (at least not on a dip test.) They did bloodwork and it was mostly normal with my liver enzymes "just slightly" elevated but not particularly concerning. Six hours later they re-did my bloodwork and my platelets had dropped by 100,000 and my liver enzymes had more than doubled from their previous "slightly elevated" levels...I was in full blown HELLP without high blood pressure or to their knowledge spilling protein. (With HELLP, there is a strong risk of liver rupture or organ failure, blood platelets can drop so low that it requires transfusions, etc., so the recommendation is almost always *IMMEDIATE* delivery.) With *most* people, the progression goes preeclampsia to severe preeclampsia to HELLP, but that's not always the case, so it's a very good thing they are keeping a close eye on you.
Regarding white coat syndrome, my blood pressure is always higher in the office than it is at home, but even so, it's never been as high as 150/100. It is definitely not good for your numbers to be that high even if you believe it's just because you are at the doctor, because it probably means your numbers creep up there when you are stressed or busy at home too. Are you monitoring your blood pressure at home at all?
Steroids are given to help develop the baby's lungs. The last week they are usually given is 32 weeks, after that, most doctors won't do them. The average onset from diagnosis to delivery with pre-eclampsia is 2 weeks, but that's just an average with people like me thrown in who deliver hours after being diagnosed and then there are people who limp along for weeks and weeks. In my second (healthy) pregnancy, I was given them at 32 weeks for "just in case" because I was having some up and down blood pressures and swelling, nothing super alarming yet but we knew we were delivering at 36 weeks and I was hoping they might help his lungs out. (He had no trouble breathing at all and roomed in with us.) Even though you hopefully will not have to deliver within 2 weeks, things can change VERY quickly and the 2 doses of steroids have to be given 24 hours apart. Ideally they do want to give them as close to delivery as possible, but if they wait until you have sky high blood pressures, etc., then you may not have time to get both doses without putting your health and the baby's health at serious risk. It's better that they give them "just in case" when a few things are looking off than you have to deliver early and not get them at all because they don't have the time to wait. So I personally think it's a really good thing they are giving you the steroids.
Me (29) DH (30)
#1-Olivia Caetlyn-9-28-09-9-28-09, 23+2 wks, emergency classic c-section, class I HELLP, IUGR
#2- Lucas Oliver (rainbow baby)- April 2011, 36+2 wks, HELLP and pre-e free! (lovenox and LDA pregnancy)
#3-Matthew, late October 2012...mostly normal, 37 wks, (lovenox and LDA again)
My blog: http://www.butterflies-and-rainbows.blogspot.com/