I’m so confused 😖

I’m 24 years old. I have a three month who I breastfeed. There’s a good chance I could be pregnant again but I’ve taken so many tests and they are all negative. My period is late by 6 days and I’ve had a small amount of light pink spotting. A few drops on toilet paper when I whipped nothing more until the other day when I got this... very stringy mixed with blood. I’ve never been so confused 🤷‍♀️ please give me your opinion 🙏