I'm up to the part where you have to go to the war at hoover dam. I start the war by talking to yes man up at the lucky 38. Is there another way to start the because with yes man everyone wants to kill me coz i have to blow up the generators.

There are other play throughs, although I believe you're too late too take a different path. You'll have to do it this way, sorry.

You can side with NCR, Caesar's Legion, Mr. House, or Yes Man. You're long past the point where you still have a choice in the matter, though.

You don't have to blow up the generator. Yes Man tells you about a second option to divert power to the fort's weather station. Taking shortcuts during the "Wild Card" quests closes that off I think.