38 weeks pregnant tomorrow

need advice so this is my 8th pregnancy I have 5 kids alive and their all natural birth the only thing is that I started yesterday at 1135pm with cramping and alot of pressure and like little shock's in my vigina like lightning something weird taht I have never felt before but it has trouble all day till now still same pain mild and dosent go away I went to Walmart walked around and I feel a little more pain and more pressure but then it slows down like I've had it like all day....what does it mean