What Causes Abnormal Uterine Bleeding?

Hi, my menstrual cycle has always been regular and i've never missed a period. I'm 46 years old and my last "regular" period started May 27 (which was 4 or 5 days early.. strange for me). I was waiting for period at the end of June but it never came. July 2nd, I spotted very little (only showed a slight amount of blood on paper when i wiped) for a few days then that stopped and happened again around July 6th (once or twice over 2 days). I hadn't seen any blood or sign of a period since then until July 20th, after a sexual experience, there was some blood. Since then, for the last 2 days, every time i go to the bathroom, there's blood when i wipe but its not even enough to need a pad. I put a tampon in this morning just in case and when i took it out, it looked like it was a regular period, plenty of blood on it (and even one little clot) but i took it out and there's no blood flowing out.. nothing on my underwear and i don't need a pad or tampon throughout the day... this doesn't seem like a period to me but it's VERY strange, especially since i've never missed a period. Again, i'm 46 years old and i don't know if this could be the start of perimenopause? or something else? i've taken 2 pregnancy tests (the last one was 2 days ago) and they were both negative. Any ideas or recommendations would be most appreciated.