Went to doctor because I was sick. Confused by what he said?

Ok so I am TTC first month. I came down with bronchitis and a sinus infection. It has been almost 2 weeks since I have had this and I went back to the doc again because a couple days ago I started feeling dizzy, nauseous and started getting frequent headaches. When I told him this along with my other symptoms he asked me if I thought I was possibly pregnant. I said I don't think I am because I just tested yesterday and it was negative and my period is due tomorrow. I was confused when he asked me this. even though it was negative do you think it is still possible to be pregnant? I tested today too and it was negative. I just don't know what to do. I'm so confused.