Is it possible to get a negative test and still be pregnant?!

So my boyfriend and I had unprotected sex on Halloween night and the morning after. He pulled out but he came unexpectedly. Fast forward to the 11th of November and I bleed lightly and spot the next day which is unusual since I always get my period for 6 days and it’s always heavy. I’ve been having numerous symptoms such as breast fullness and soreness with excruciating pain, random heartburn I’ve never experienced before and I’m vegan and eat healthy. As well as headaches everyday for a month and I’m so easily tired and so much more. I swear I feel like I’m pregnant but I took a test and it came out negative. Is it possible to have low hcg and get a negative test and still be pregnant ? Has anyone who’s been pregnant experienced anything like this ? Need answers !