Labor or ?

Has anyone had this happen around week 31 during pregnancy? At random times all of a sudden I will get this back pain that feels like a menstrual cramp while my stomach tightens and then the tightness will ease but the back pain is constant until all of a sudden there is no more pain or tightness? I’m also leaking colostrum all of a sudden and have tons of pressure and pelvic pain. This is my third pregnancy but my body didn’t go into labor on its own with my previous two so I really don’t know what the start of contractions feel like. This pain takes my breath away and will radiate to my underwear line as well. It’s happened like 5 times since Thursday. Today it’s happened 3 times. Once when I got up in the morning and once after getting groceries and now just a few minutes ago while I was sleeping.