How old are you? I just got a period 18 days after my last one. It's the first time this has happened. However, most of my periods have been less than 28 days apart, although the two before this last one were 40 days apart. I'm 47, so I'm hoping this is just hormonal fluctuations associated with menopause in my future.
Many months ago I was having very painful periods that centered in my lower pelvis, but now there is no pain with my periods at all. No weird discharge. I had an ultrasound Sept 2016 and my uterus was supposedly very good looking and thin. I have a few fibroids but they were found long ago.
Definitely speak to a doctor.
If youre having two periods one month and no period the next, thats normal but two periods every month could mean you have an infection or another medical issue. You should definitely get that checked out by your doctor and if it is normal they can at least prescribe you a stronger version of midol for the cramps.