Doctor..i had intrcourse in last week of July..then periods For next3 months lasting 7 days,,,butt missed it for d month of November,instead ha d spotting of brown old blood for abt 12 days around d tym of my periods,..did hpt..it came negative,,,currently with back n neck pain...lately i ve been stressed out...can this be possibly pregnancy??my periods r not regular as such...m21yrs old..plz help me