Ive got period type cramps and low back ache but period not due for 2 weeks?

A couple of things: Often cramping is associated with ovulation at mid-cycle. Some women also report that even if they typically get ovulation pelvic pain, it is different if they become pregnant during that cycle. So ovulation and pregnancy are considerations. Fibroids or ovarian cysts can also cause mid-cycle pain. Do a home pregnancy test if you miss your next period. Good wishes:)

Mittelschmerz: Or pain in the middle of your cycle. This is pain caused by ovulation. Every month when you ovulate you have an egg follicle rupture releasing an egg that can be fertilized. Some women have the pain and cramping you describe when this happens.

Possibly ovulation: In a normal menstrual cycle, ovulation (release of the mature egg from the ovary) occurs 14 days or 2 weeks prior to the beginning of menstrual flow. This can be accompanied by cramping and low back pain and even light spotting. The term used to describe these symptoms is "mittelschmerz" and means "middle pain" for pain mid-cycle. It is likely totally normal.