Sure does sound like endo...
The pain worse around period time
Pain during intercourse
More pain of a night ....(seems our bodies are more pre-occupied during the day, night time we apparently are more aware of the pain so a BIG YES to night time pain, up 1am, 2am 3am, strange how the body works isn't it..
Fetal position and crying for hours....wow you're bringing back some of my own memories, they fit to a tee
my emergency visits to hospital always in the wee hours of the morning....
I would describe my endo pain going back 3 years now as above, but also it's a heavy deep throbbing, sometimes stabbing pain
Along side Endo I also had
AdenomyosisIt's hard for me to really be spot on with the description because at the same time this was going on I had a burst appendix that was not diagnosed,
the agony oh my god, 
I've never experienced anything worse so I can't tell really if all this was from the appendix or Endo and Adenomyosis because I had a laparoscopy to remove both the appendix and the Endo Laser Treatment and after that 99% of this pain disappeared. So it could of been either or all of the problems.
Laparoscopy was a very simple operation for me, depending on your Gyno they will either cut out the endo or laser (as I had done) I've since had two more laparoscopies and I have no Endo at all, my pelvis is crystal clear, so the Gyno did a Fantastic job still no return.
Couple things I will mention:3 Ultrasounds I had in my home town showed nothing (all clear)
Gyno in my home town told me all my problems were in my head
nothing wrong with me
(at that time I had a burst appendix) but no apparently I was perfectly healthy................
:angry
Also my appendix pain was all LEFT sided, most think right sided, but it can be referred pain, hence Doctors not considering it an option, but wow
how wrong they were...
ultrasound failed to show appendix too because it had burst and not diagnosed quickly it had started to form adhesions around it ( apparently the bodies way of protecting itself against infection, it covered the diseased section so it doesn't spread to other body parts )
So I Ventured into the City to find a better Gyno and he also Performed a more in-depth Ultrasound (sorry don't recall off hand the correct name for this ultrasound) anyway again Endo was still not picked up, all he could see was a Fibroid (benign)
He discussed in depth how there were debate between practitioners on how to diagnosis Endo and his opinion was it can only be correctly diagnosed via a laparoscopy... and my description fit to a tee so he had a high level of suspicion..
Sorry babbling again
What I'm really trying to say is despite tests showing everything normal (besides the Uterine Fibroid, which many women have and not a concern) is it took a very experienced caring Gyno to work out my problem back then, picking up my burst appendix was a god send, I could have died
So if your Ultrasound comes back clear don't be disappointed, try and research more on Endometriosis Experts
in the hope they will perform a laparoscopy despite Ultrasound testing Negative
Sammy