Doctor Update: Period started 3 days late

I was supposed to start Monday Nov 5th. but I was late up until today (Thursday 8th). I usually have a few PMS symptoms before it starts but this time nothing at all. Today it starts and I'm going through some of the worst cramps in have ever felt. Lower abdomen and lower back are in excruciating pain. So much so that it even hurts my rectum. I've never felt this much pain before. I dont know wth is going on. I can't get comfortable no matter which way I sit or lay. Can anyone offer any advice or have an idea of what is up? I dont like going off into google because that just always exaggerates and basically says one is dying. Hoping someone out here has an idea or some kind of personal experience. Husband is already getting me an appt (he works at a clinic) but that probably wont be available till tomorrow. Thank ya'll in advance.

Update:

So my husband spoke to the doc at the clinic and she has given me a referral to a gyno because she highly believes it could be Endometriosis. I've never considered the possibility if having this but we have been ttc for 2 years now with no success. I tried clomid for 2 months but I gave up on that after the doc found that I had a blocked left tube with a dominant left ovary. We just pretty much gave up on ttc if our only option really was to risk surgery and pump my body with hormones on top of the thyroid hormones I already have to take. Anywho, theres a possibility I have endo but its yet to be confirmed.