Why some times during sex I just get soo dry?
Well that could mean 1) You have been going at it for so long that you become dry and raw 2) You aren't as turned on as you were when you started 3) You are older (meaning like, late 30's and on) and you can't produce that fluid as easily anymore. My suggestions would be work on foreplay a little bit more, get rid of all other thoughts but sex when you're doing it, use store bought lube.
unless your really turned on
your vagina doesnt produce much natural lubricant
so using a personal lubricant such as KY is a good idea
many people use lubricant to help with sex
also as the above said
if your not too turned on try to work on foreplay for a bit longer
drink more water..drink a lot more water and start using lebercint
because you are not turned on, and you are not enjoying it.
Not turned on enough to do it