Do you think I’m pregnant?

My husband and I made love when I was fertile around Sep 12. My period cycle is always normal and follows my calendar. On Sep 21-23 for only 3 days, I had a spotting of a dark brown to dark red but not my normal menstrual flow. Next spotting was last Nov 9-11, but no menstrual flow. Only dark brown diacharge with watery slimy fluid. From end of Sep until now, I sometimes feel dizzy while walking or doing some errands. I had tender breasts and cramps also. But I did took around PTs but came out negative. I took it late afternoon or evening after work. I am really hoping that if I am not pregnant, I hope this is not something serious. Please share your thoughts. Thank you!