PvT 2 medivac timing


I'm a protoss player (diamond) and I've always been struggling vs terran. Recently, when the terran early expand, I've been doing a 1G expo followed by 2G robo for obs and then rushing for +1def and charge to counter the 2 medivac push (while teching toward templars).

The fact is whatever I do, I just straight up lose if the terran doesn't mess up his first agression. I don't really see any other player struggling so hard with that push, so I must be doing something wrong....

If I manage to survive and take a third, the game become even again...

So my question is, how do you defend this?

ps: I'm french so please forgive me if I messed up with my english