Mid pregnancy spotting/bleeding?

Has anyone else had bleeding at 18 weeks? I'm about to lose my mind. I've called the hospital and the doctors office and they say to watch it and wait (I have drs appt Tue). However, I've still been spotting since Wed. night. Sometimes it seems to get heavier then it turns into pink spotting then to nothing and back again, but nothing severely heavy. I'm also not in severe pain. Now I'm paranoid about every little twinge of pain I feel, but I really can't say I'm in PAIN. At this stage, if I were having a miscarriage wouldn't I KNOW it? Also, I'm surprised about how non chalant the nurses are about this seeing as how bleeding is much less common at my stage of pregnancy. I thought maybe it would go away, but now I'm feeling helpless because I don't know what to do or what may be going on. Any help?