Red Urine

Hi ladies. I’m about 20.5 weeks. I just had my anatomy scan on Monday and all looked good with the baby. This morning I had sharp pain in my right lower back, which I figured was constipation pain. It went away after about an hour. Tonight, around dinner time, I peed and it looked red. My husband said it looked more brown than red, so I drank a liter of water, figuring it was just dehydration. Went to the bathroom again before bed and it’s lighter pee, but still with a red tint. If my morning pee is red, I’m going to call my doctor but has anyone experienced this? Thank you for any help you can provide! Worried about my baby :(