How can a husband overcome his insecurity in this situation?

Hi, I asked earlier so I apologize if you've read it before. We've been together for 6 years and have had ups and downs. She's a great wife and friend overall. We've had problems over the past year. She's made some hurtful comments, doubted me as a husband, criticized me frequently, and had a flirtation with a guy at her work. We've worked it out but in a way it has brought back memories of when she dumped me years ago when we were dating. She dumped me the same week my parents each told me they were getting divorced and so would no longer support me in college (each wanted to hurt the other through me). That time I worked hard to win her back after getting a job to put myself through school, but she in some ways was reluctant to get back together and at one point told me she would date other guys for a while even when we were back on. I accepted this and fortunately she never did date others, but I think it started a tendency of mine to feel very insecure and to walk on eggshells around her. Part of what has always bothered me, both then and now these recent problems, is that my wife sometimes thinks I overreact to things and am insecure. She sees a lot of what she does as harmless and that I am insecure or dramatic. She says she didn't tell me about her work flirtation because she knew I'd overreact. I think through our talks I've gotten her to see that much of this is a real problem and not just in my head. But at the same time I want to be able to meet her halfway and work on my insecurities. I know I still walk on eggshells around her even today, and any complaint she has I feel great pressure to fix right away because I never saw it coming the first time she left me, or even back then when she sat me down, said we were back on, but told me she wanted to see other guys. I thought she was going to say something about us always being together. How can I be less insecure as a husband? How can I get the confidence to be the man she wants me to be?