It sounds like you really don't want to be pregnant, so I would follow up checking to see if you are pregnant with a discussion with a doctor or someone at Planned Parenthood about contraception to make you sure don't have any more scares.
If you get a positive pregnancy test, THEN start thinking about what to do if you're pregnant. I'd get a test and find out soon. I'm sure you could get help from Planned Parenthood for that as well.
I felt like my period was going to start any minute, and felt that way for an entire two weeks before my period was supposed to appear. And then it never did. My symptoms included back and leg aches, moodiness, fatigue, cramps, upset stomach, and a lot of hunger and thirst. If you haven't had any symptoms at all besides a weird period I would guess you are not pregnant.
But obviously every woman's body is different so I could be very wrong. Just relax and take a pregnancy test, so that you can quit over-thinking everything. I know that can drive you nuts! If it's positive than you have an answer. If it's negative take another in a week or two just to make sure.
Are you possibly recently off hormonal BC while TTC? When we began TTC #1, I stopped BC, had a few normal cycles, but it seemed that when we actually began actively TTC, there were quite a few changes in menstruation in the months prior to conception.
Additionally, implantation bleeding is a very sketchy subject. Personally, it's not something I have noticed with either of my pregnancies; although the first was planned and I was watching alertly for any sign; and in the second case I knew we'd had unprotected sex near ovulation so also watched alertly for any early sign. If your bleeding occurred near the time of normal menstruation, while it may be due to changes in cervix/etc., I doubt it is "implantation bleeding," and pregnancy test results are typically reliable as soon as the first day after a missed period. Therefore, if you feel your bleeding may not have been actual menstruation but was at the appropriate time, I'd suggest a test.