Sounds like two separate problems, so dealing with each in turn might help it seem less hopeless?
First you have a problem with having to pee a million times a day and at night too, which adds sleep deprivation with it's own problems.
Has your GP done anything about the bladder problem? When the sonographer said your bladder was filling up quick, perhaps it had only half emptied and the sonographer thought it had just started filling up from zero contents and got to half full already?
I think that it's common to only half empty your bladder, as we get older the bladder gets bigger and floppier and just doesn't squeeze out the contents, we need gravity more to get it all out. Sitting forwards or pulling your knees up can help with a no2 (apologies, tmi) and there are positions that help with peeing too, to get more out.
I think your doctor should be doing something, prescribing something to calm down the bladder, sending you to physio. Unless you're drinking huge amounts every day then each pee must be small? But the ultrasound showed the bladder and it wasn't tiny or she would have said, so your doctor needs to help you find out what is going on.
Then there is the cervix and lining. Did the sonographer mean the lining just inside the cervix? That's where mine was measured couple of months back. I think anything over 6mm is investigated, so as she said, it's only just into the thicker range, it depends a lot on how accurately the sonographer puts the little crosses on the screen, but they'll do further tests as a precaution. I'm sure it will be fine, the wait is always agonising, I can sympathise with that!
Has the bleeding been coming from your cervix? Mine has very thin skin on it that tears and bleeds any time a medical person comes near me and did that all my life, will be thinner now. However relations with my hubbie never make me bleed, so I do blame them and their medieval looking tools.