Whenever I had trace amounts of blood in my pee it was a UTI. Mine don’t show up on dipstick tests, only sent off to the lab but you say it came back ok. In that case I would try to drink plenty of water and have it tested again soon as the last thing you want is a kidney infection.
Oh, and cystitis has been mentioned. I don’t know if you can have Cystopurin when pregnant, but if you’re not in any pain then I would think it’s just rehydrating you need. Cystitis is similar to a UTI, but is more irritating of the bladder rather than a bacterial infection. I’m pretty sure this can sometimes cause blood in the pee, but probably not in large quantities. The best way to get rid of that is simply plenty of water. When my infections/bouts of cystitis got really awful I would be drinking 3+ litres daily to flush it through.
Avoid caffeine, tight fitting underwear (and try to only wear cotton), tight clothes, sex and don’t use any soap (not even stuff designed for down there) just use water to wash with
