Wth is going on with my body?

Hope
I missed two periods, neg hpt's, couldn't get in with a doctor for bloodwork because of Insurance issues. Then received what I thought was a period, didn't last as long as usual though and didn't seem normal. Called DR and they agreed to see me on Tuesday (4 days from now) well now I began spotting brown tonight. What could be going on with me!? Any ideas?