What Causes Bloating, Severe Abdomen Pain And Gastritis After Menstruation??

Ok, so my period ended two days ago and I have been having pretty bad stomach pain, some weight gain, bloating, (very smelly, which is unusual for me) bad gas, and some weird stools. I am very uncomfortable and have been this way for about a week or two, but attributed it to my period and that coming on. What could this be??? I am slightly worried but don t know if this will just go away on its own or if I should see a doctor. If it makes any difference, my period lasted about 3 days, which is short, but mine has been this way for about 6 months.