Hello I Am 21. I'm Very Worried That I Am

Hello I am 21. I'm very worried that I am pregnant. I haven't had a regular period since November. Since then, I've only had spotting in mid-February. My stomach feels very tight and stretched. It feels hard, but only under my belly button. I've taken countless home pregnancy tests and they're all negative. I am so afraid to go to the doctor because the negative tests are making me feel like I'm crazy. Please help me.