Blow jobs!

I’m married. Been with my husband for 4 years. I don’t like giving head. But clearly he likes it. I have done it maybe 3 times our whole relationship. But the only way I can do it is if he wears a condom. Which I don’t think does much for him. How can I get to the point of not using a condom? I mean I have tried but it’s like the moment it starts I freak myself out and start to throw up. I know I’m the only one he’s been with since we have been together. But I still just think about all the other people he has been with. Any tips? It’s hard to not think about it.