Please help! TMI warning

I am 29 weeks pregnant and 3 days as of today. So today I woke up to pee at around 5:45am and I had blood in my urine. I have had one pregnancy go to 36 weeks n hes a wonderful healthy boy never had any problems so I automatically assumed the worst. Called my husband at his job n said I need to go to the ER right away. We went n they took 2 urine samples, had me on monitors, did a kidney n bladder ultrasound, took blood work, had me stuck to an iv, did a catheter and about 4 hours later they said theres nothing wrong with me and sent me home. Baby was healthy so I'm so relieved but I'm still peeing blood and I'm just so worried. They told me theres no uti no stone that they could see or anything no bacteria in my urine. I felt better at the hospital because I could hear babys heartbeat but now I'm so stressed n freaking out i dont want anything to happen to my baby boy. Has anyone had this happen and been okay? Did it go away on it's own. Theres no vaginal bleeding only in my urine