colonoscopy, endoscopy, crohn's???

ok my drama had started about a month ago. for as long as i can remember, i have been plagued with periods of serious constipation or violent diarrhea.  well a month ago i had a terrible episode of diarrhea.  it was bloody and had mucus (sorry for the details) and lasted for hours.  it was just awful.  since it was bloody i went to my regular doctor who drew about 8 vials of blood and referred me to a GI.  while i waited for my gi appointment, the blood results came back with everything normal except low red blood cells and extremely low vitamin b12.  my doctor said this pointed to crohns and started me on the b12 shots.  since then i have seen my GI, who also mentioned crohns due to the b12 and scheduled a colonoscopy.  well i went for the colonoscopy yesterday and he said evi had a spastic colon and IBS, but he took biopsies to double check but that now he wasnt thinking crohn's.  he has me scheduled for an upper endoscopy on monday.  
what is he looking for? i was so relieved to hear it wasnt crohns.  but does anyone have any ideas as to what may be causing my symptoms, particularly the low b12? thanks so much in advance!

[waffenamp]

Do yuo smoke cigarettes? Recently My guts have been messed up also. They have been fine untill I got stressed out and smoked a little weed and a pack of cigarettes the other day. Well on the first puff of the cigarette I felt like I was gonna have diahrhea. I held it in cause I was at a friends house. I continued to smoke cause I thought it would help my stresss. Well by the end of the day I had smoked about a pack. Ever since then my guts have been in cramps, and feeling full and bloated. I know this is from the smoking because this has never happened before, and all of a sudden it happens when I decide to smoke cigarettes. Well its been almost 2 weeks and im still bloated and feeling crampy with some diahrhea, and constipation. I know the nicotine or cig chemicals messed up my guts. Im hoping they dont stay like this from 1 pack of cigs

[confusedgal411]

no, i dont smoke cigarettes or weed.  but thanks for your suggestions