I'm a IBS patient, and usually, it depends but it is very usual to go straight to the bathroom right after you've eaten. Usually for me 10-20 minutes after I ate, i get pain or go to the bathroom.SO I suggest that you might IBS, but to be sure you should seek a doctor. Specially a Gastroenterologist.
this sounds a lot like what seems to happen to me. I am going to the gastroenteroligist tomorrow in hopes of finding some info. I will keep you posted.
Also, my mother has Crohns Disease which is what my symptoms are similar too but i have been told that it is not herriditary. Again i will keep you in my thoughts and let you know what i find out.