Relationship advice

Okay so I need some advice. I know I post on here a lot but the friends I have don't understand. So I have this amazing fiancé! Been together almost 5 years and  e have a 3 year old daughter together. He treats us both very good. Home every night,always there to help,spends time with us doesn't hide anything for me unles it's a good surprise :). I can go thru his phone or any of his stuff at anytime. I'm mean sure we have our disagreements but that a very rare and when we have them they are over in 5 mins. So why do I feel so obscure,emotional? Why do I feel not pretty enough or have negative thoughts running thru my mind? Why do I feel like crying in a snap of a finger or like he doesn't want me? He shows me tons of affection. I just don't get why I'm like this?