What Are The Side Effects Of Emergency Contraceptive Pills?

hello. i recently forgot to take my birth control the past two days. i am sexually active and this morning i woke up to use the bathroom and my vagina was bleeding. it was dark red and slimy.my period was about 1-2 weeks ago. i took a pregnancy test this morning and it said negative. is it too early for that? im not sure what to think. i also have UTI quite frequently and know that it mayyybe could be a sign of kidney failure.