I have been going out with my b/f for 6 months. He has trust issues which I can kinda deal with.?

But I get so frustrated with him when he doesn't believe me. I am very indecisive so I constantly change my plans at the last minute. He always gets on my case for it but that's just how I am. We have recently had a huge fight over this and he was quick to accept my proposal to see other ppl. I feel like I messed up and I don't know why.