Measuring WAAYY ahead

I'm 33 weeks pregnant, but today at my appointment I'm measuring at 38 weeks! Baby is head down. I've had a lot of pelvic pressure as well as fainting spells. Today my ob discovered I have a BV infection, which is being treated with antibiotics. She said that once it's gone the pressure should go away, but she scheduled me for an ultrasound, to check my fluid and baby's size, Friday with a follow up after. I'm really worried because I've been measuring big this whole pregnancy, but only by a week or two. Has anyone else had this much of a measurement difference? What did they find out? Could my due date be completely off???? She also is now categorizing me as a high risk pregnancy. I'm panicking so bad. My first pregnancy was so unbelievably easy and this one has been so rough. Help! Any advice or experiences!