Jennifer, yoou have my every sympathy! My son Charlie does exactly the same thing.

I have 2 methods....and it depends on how much time we have as to which trick I use!

If we have the time (and dependant on where we are a little as well) if he arches his back and starts a tanty, I bring him back out of the car, let him stand next to me at the car door, and see if wants to climb in by himself. He will often haul himself up into the seat (takes ages) and then he will let me strap him in quite happily. (If I already have the ignition/music going in the car this works well).

Other times he will just continue the tanty whilst at the side of the car, so I walk him by the hand away from the car.....if he thinks he may miss out, he will then drag us both back to the car and let me pop him in.

If, however, we are in a hurry: bribery! I alwasy have a stash of cruskits and arrowroot biccies in my bag, so I get one at the ready, offer it to him as I say "Straps on now matey!" and plunge him in quick! (He is keen on his food, so this treat often works, and is quick!)

Good luck......I promise you it IS just a stage. Olivia went through it too (to a lesser extent than Charlie......it took only a few weeks for her to "grow out of it" but she was talking well, so I could reason with her, whereas Charlie isn't......)