Hello
I was wondering if I had IC. So here's what has been happening to me. A few months ago when I was diagnosed with Endo. I always had to use the bathroom like 15 times a day, because every time my bladder gets full (I drink A LOT of water) I would feel this dull aching pain deep inside of me. But after I empty my bladder I would feel a little relief, but the pain is still there it's just not as intense. Now months later I don't pee as often, but when I do; I would pee and the pain is reduced. I don't wake up in the night to pee and I use the bathroom about 5-7 times a day, depending on how much I drink. I don't feel any burning or UTI sensation. When I would go to the hospital my urine test would be normal no blood or protein. The chronic pain I feel is hard to describe it's like when my bladder is full it's pushing on my uterus causing more pain. When my bladder is empty the deep pain is still there, but mild. But I don't have that urgent need to pee like everyone else. I can hold my pee in for a long time, only if I drink and have to pee because my bladder is full and pushing on my uterus. Do I have IC or Endometriosis on or around my bladder or maybe on my uterus because these organs are so close.
Interstitial Cystitis (painful bladder syndrome), FODMAP diet and Endometriosis 
Anyone have Endo in their bladder? 
Endometriosis and Interstitial Cystitis
It sounds more like IC from what you describe. Endo in the bladder is working on a monthly cycle like all endo, so it is active when you have a period and that is when there is a noticeable change - blood in the pee turns it pink if endo is inside the bladder and bleeding - but that wouldn't happen in between periods.
There are infections that do not cause burning or pain when you pee or afterwards, only certain bugs have that reaction - and some do not, so having pee checked regularly for infection is a good idea.
Cysts pressing on the bladder, adhesions attaching the bladder to other organs like ovaries and uterus and even bowel can cause changes to pain levels between a full and emptied out bladder.
Short term aching can be a sign of kidney or bladder infection but usually ccompanied by fever and unwellness too.
Long term could be a prolapse of the bladder, cysts pressing down on the bladder, endo stuck in the cavity between the bladder and uterus etc.
You need to speak to your GP and ask to be referred to a Urologist who deals with bladder endo, as that is a possibility. If you have already had a recent lap op to map the locations of endo growth at that tie they can check if there was anything endo wise in the cavity between the bladder and uterus. An ultrasound scan can check for cysts and sometimes spot if an ovary has got stuck to the bladder too which would indicate adhesions.
There are tablets you can try (- several kinds) to see if any of them can give you back more bladder control. It could be that you are not filling up the bldder fully before your brain gets the message that you need to go pee - this can be caused by a disruption to the muscle contractions tht normally do a good job. They are called bladder spasms and while you cannot feel the muscles actually having a spasm, they are not pulsing in the right order and it is easy for the brain to be told bladder is full when infact it is not.
Bladder spasms can come about from trauma, infection, and proding and poking during surgery for something near by.
Dont suffer with this in silence - bladder problems for all sorts of reasons are VERY common in men and in women. You'd b surprised just how many people are walking round with bladder problems and you haven't a clue about it. Do speak to your GP and get the investigations rolling. Something is causing it, and not always poss to find a solution but you won't know till you have exhausted all possibilities. Best of Luck