Help?

I need help. My period is 27 days late and my mom and I are slightly flipping out. The only signs I could have is congestion, but the pollen count were I live is very high and I have allergies.

I have light constipation but can that be caused by dehyrdation? I dont drink much water at school because the vending machines are expensive and water fountains at my school are horrible and nasty.

I have been really stressed recently since I just had to transfer schools and I am starting standerdized testing earlier this week.

My mom found out and is being suspicious and untrustworthy for some reason. She is saying she is going to buy me a test when she knows I am not sexually active and I am only 14. I don't have a real doctor I go to besides a normal pediatrician. I have no real adults I trust enough to talk too. I don't know what to do.

Is stress and school and just overall emotions plus dehydration a possible reason for period to be this late? Anybhelp please? Sorry if I seem "uneducated" or ignorant but I have honestly had no sex ed or anything since my school doesn't teach it anymore.

Please just any help or anything. I don't know how to react to my mom or how to react to my period like this or anything. Help??