So your GP does think it's likely adenomyosis. When you see gyne ask for an MRI as its pretty good at detecting adenomyosis. Plus the ultrasound has already given a clue with the heterogeneous uterus.
In terms of management, I'd probably look at the blood in urine as seperate to the gyne stuff and make sure your GP investigates that throughly. Something like an ultrasound of the bladder area could help, an abdominal one to check kidneys etc. Did you get other urine tests done?
I would look into getting a mirena/IUS (ideally before the appointment as it is 1st line for good reason for this and gyne will suggest, so its good to get adhead of it and discuss all other things to help alognisde it). The mirena is more effective at thinning the uterus lining, preventing growth of lesions and the lining, and can stop or make your period much lighter, so there's less cramps as well.
For the insertion, I would ask the GP surgery prior to your mirena to make sure you have pain control. That can be all of or some of the following: numbing gel, an injection into your cervix, lube etc to make the insertion the most comfortable. Also take paracetamol and ibuprofen 1h before the procedure to help.
For the pain talk to your GP about them prescribing you NSAIDs such as naproxen or mefenamic acid, they can prescribe some for like the 3/4 days leading up to your periods and then during it as well (they work better if you start taking them before the pain/period starts). They are anti-inflammatories so help to reduce pain, etc. It's very worth looking into getting that prescribed.
You can also use and I'd recommend using tranexamic acid, it helps with the bleeding during your period and can massively reduce any heavy bleeding and again start it 1-2 days before your period as well.
https://www.nhs.uk/conditions/adenomyosis
The link has good info you might want to read.