Fundal Height measuring ahead??

My uterus is up where it should be at 18-20 weeks and I'm only 13 weeks...also I've been feeling baby kick so hard up by my belly button that my friend could feel him/her when she felt my belly...has this happened to anyone else?? This is my 4th child and I have always measured exactly on the week with all 3 of my kids. Also on all scans except one (I've had several due to an SCH) baby was measuring right on track for my due date.