Anger outbursts

I have an issue with when me and my fiancee get into an argument I will almost certainly lash out and attempt to break something, I have thrown pictures, thrown my phone, and punched holes in walls all because of this and now its got to the point where I think she is going to leave me before we get married. I am also worried because she is pregnant and I do not want to like this when the baby arrives. The reason I react this way in arguments is because I feel she doesn't trust me, and she has every right to because at the beginning of our relationship I messed her around. but is that really something she should hold on to and accuse me of cheating? This is why I React badly because I have done everything I can to show her she is the only one for me , I don't expect her to trust me like I trust her, I just want her to trust me enough that I can go to work and not worry about her thinking I am cheating. Am I asking too much of her? And how can I deal with this frustration without reacting the way I do?

Thanks for taking the time to read my post and I look forward to reading your responses