adu

i am 22 year old.
I have had irregular periods before.The end of my last period was October 8, 2012. than next month i was not got my period. so after 10 days i took some aryuvedic tablets for 2 day. and than next day my period was start on 19th November, 2012.
but now after that month again my periods are not coming. date should be 19th dec, 2012. but its already 20 days and i am not getting periods. and i have had 10 negative home pregnancy test. I don't know what is going on. and i am very tensed. Could i be pregnant ?
eagerly waiting for a reply .

Since last night, just before bed, I went to the bathroom and only a little urine came out. And it was weird because as I was going I kept feeling pressure so I kept stopping myself, but once it was all out, I pushed as hard as I could to make sure it WAS all out, and nothing came, even though I felt like I still had to go to the bathroom. I woke up 4 hours later needing to go to the bathroom really badly, so I went to the bathroom and emptied my bladder without pressure problems. Lots came out, but I still feel a strong urge to go!! It's starting to worry me, as this feeling is sort of painful. What could do this be? It doesn't sound like urinary tract as it's only painful because I can't urinate and I want too! Only symptom I'm aware of.
is it pregnancy symptoms ??