Advice Please?

VIIXXXIMMXVII🎀💕 • FT young mom & dad to a Babygirl born July 31st,2016 @ 39w. 6lbs even 19in long. ❤ She has changed our life before making an entrance🙌 Thank God for all we have :)
So. I'm 17 years old (18 in March) I'm engaged to a wonderful hardworking man and great daddy to our precious 6 month old. We have a good life I mean as far as necessities go we have it all. I have a good head on my shoulders I know what I want. I start school this May to start earning my diploma to become a MA. Etc etc. I just have NO damn confidence. Like I know I'm not A bad looking person!! I have a great heart. For example I see a girl and automatically start comparing. It's literally tearing me up inside. I feel worthless and I guess you can say ugly. It's so awful.. Do any of you ladies get like this from time to time? Mind you some days I'm just feeling myself but say if we went out and I seen a pretty girl or something I immediately start comparing.