I had been feeling off for about a week, nauseous, tired, headaches, etc. and my husband and I were beginning to think I might be pregnant. I took a test 2 days before I was late and it was negative, but we still weren't sure. We were having sex the next day and a mass of white "goo" came out. I started my period the next day(about 3 days later than normal). It was brown and bright red and the cramping in my back was really bad the first night but has gone away now. I'm just wondering if I was pregnant and had a miscarriage or if it was just a coincidence that I was sick before I started?

That "goo" sounds like fertile cervical fluid or a yeast infection, semen, etc... it could be a lot of things but not likely connected to an early miscarriage. The only way to have confirmed a loss is to have blood work, ultrasound, etc. so you may never know. If you were only a few days late and IF you miscarried, if would have been a "chemical pregnancy" and you would not have experienced symptoms because the egg would not have had time to attach to the uterine lining, which begins the hormone shift your body would go through.