Don't base your pregnancy on your LMP cos it is never accurate even with a regular cycle. That's why ultrasound is needed to measure the size of your fetus and also to estimate your EDD. It's really common so nothing to worry cos all my pregnancies are/were the same as yours. That's also why gynaes will only start seeing pregnant women on their 8th week of pregnancy onwards. By this time you can see your fetus and hear it's heartbeat.
Yup thrs a chance u ovulated late. Happened to all my pregnancies, always get pushed back a week or 2. Dont worry so much, stay positive! Good luck!