RED BLOOD DOT ON TISSUE...wtf?

Shanice • I`m 22. Engaged.
Okay so I went to the bathroom tonight & there was a red blood DOT on the tissue when I wiped (I probably should've taken a picture). I don't know for sure if I'm pregnant or not & also let me tell you guys about what happened after my period.
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My period only stayed on for 2 days (never happened before EVER). 2 days later I was spotting & then it stopped....then I spotted again 3 or 4 days after the previous spotting. I don't know what this could be. I haven't been able to take a test yet because I went to 2 stores & they were both out of pregnancy test (such a bummer).
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Just in case you guys ask, no I have not been stressing & I didn't have sex either. 
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Has this happened to anyone?