dreams are usually just metaphors for our inner emotions, your fear of going crazy is obviously being portrayed within your dream, which is just your subconcious mulling over thoughts within your head.
Last night i had a particualrily disturbing dream too. I have a real problem with the concept of death and loosing someone close to me. I dreamt i was inside a big warehouse, then soldiers came marching in and we all had to run out of the building, as we all ran out, all of my college tutors ran to the otherside of the building to try and see what was going on, but the building blew up, killing one of my tutors who i really like, it was horrific, and i felt so insanely upset, when i woke up it was such a relif, but still, it was just my subconcoius releasing some negativ engergy, dont worry about it. Your not going to go insane, dp doesnt do that to you, if anything dp is the opposite of insanity, its being to sane, being over concious, over cncious of everything.
good luck my friend!