What Are The Symptoms Of Pregnancy In Irregular Periods Case?

G My name is Nicole and I have a few questions, about early detection signs of pregnancy. In my case, it s very hard to tell if I am or not. Reasoning b/c I usually have a menstrual every 3mths. However, the last menstrual was in Aug. My primary OBGYN has informed me that if I don t have a period with in 3mths that she would prescribe me medicine to make me have one. So November comes and I started to notice ONLY a brownish spotting which is very faint but still showing; which is known as Implanation Bleeding. Knowing that you can still ovulate w/o have a menstrual still is a chance of pregnancy. Other symptoms that I ve notice is, the Hot Flashes, Nausea but can t throw up, Abdominal Bloating, Mild Headaches, change in appetite, and frequent going to the bathroom. I took a pregnancy test which was negative but I believe that it was too early to detect the HGC hormonal levels. My question is, I ll be taking a blood test this Friday to get a more accurate result, but if that still comes up negative, what could case this? But the last time that I had my menstrual I didn t feel like this, and a Woman knows her body due to unusally changes if this has never occurred. Thank you So Much