Period?

I recently posted about when should I test again. Well this morning I woke up with horrible back pain and a headache. I went to the bathroom and I think it could be my period but im not really sure. It feels different. It was three days late. It just doesnt feel like a normal period to me. I feel really sick to my stomach. I have horrible lower back pain and headache. I never have these things on my period. I usually just have cramps and bloating on my period. It is not very heavy of a period either. I am also very emotional. I go from crying to being very cranky. With my period I usually have a little of thsese symptoms the week before it starts. I dont know it just feels wierd. I wonder if this is just a really nasty awful period or am I preg? This is driving me nuts.