So about a hour ago I went for a pee. Half way through (mid stream) I had a sudden pain in my mid to low back. It was bad enough to stop my pee mid flow and I had to stand and breathe through it for a minute or so until it passed. I then was able to finish my pee 
Historically I have had trouble with kidney infections etc so I have test sticks at home. So when I went again about 5 minutes ago I tested. Everything was perfect. No protein, white cells, ketones etc and I am well hydrated. However the blood reading rocketed up right away. I've never seen it that high without something else showing up or me running a fever etc. I definitely do not think it's a infection.
I'm 36+5 weeks and last week baby was head down, 1/5 engaged. MW suspected I could go early due to position etc (but it's my first so I have no hopes pinned on that)
I had intercourse twice today in the morning , but extremely gentle as I have SPD. I've also been on the birthing ball a lot as it helps with my heavy pelvis feeling.
I am going to test again when I next pee and there is anything Ill definitely phone someone (out of hours or on call midwife do you think?)
My question is, as Google shocking provided no answers, could this be a sign of things changing in my cervix and it's just got mixed with the urine? Has anyone had this pre labor?