So My Last Period Was September 14 And My Menstrual

So my last period was September 14 and my menstrual lasts for 5 days, I'm sexyally active and on Oct 14 when my next peeiod was due but my period never came. I started having pregnancy symptoms ans i started spotting on Oct 17 and it ended the 20th. I took a pregnancy test and it came out negative. I waited until November, still having symptoms but my period still didn't come I was still spotting/light bleeding. I went to plan parent hood and they did a urine test and it still came out negative. So I took their word, but I feel the same way and I feel a heart beat in my stomach, it matchest mine but mine is a little faster and I'm confused to why I feel this way but getting tested negative. I never had a problem with my period until now.