During my second trimester, after having multi orgasmic sex, my face breaks out in dark splotches all over. what is this and how do i prevent it?

Well, don't have sex: But that's not really an answer, is it? Your facial flushing is a common side effect of capillary dilation that accompanies sex, embarrassment, certain kinds of food, and many other stimuli. There's really nothing to do about this as this is a normal physiologic response, more or less in certain individuals, and perhaps more with pregnancy. Forget the flushing and god bless multiple orgasms!