Ways to improve self confidence??

Aly😽👸🏽
Lately I feel I've been struggling with my self- confidence. A couple years ago I was always so strong about the way I feel and see myself, but as the years have gone by Ive felt myself being more insecure. I did go through a tough break up a while ago and maybe that's apart of the reason for my insecurities. I have an amazing boyfriend now that treats me amazing, like no guy has ever treated me.. But I seem to always feel so threatened by other girls and get jealous so easily when it comes to him (it'll be over the dumbest things that I know don't mean anything). I just always have that mindset that every girl is out to ruin my relationship. I can't tell if that's just normal or not but I need advice on how some of you stay confident with yourself?? Ways I can work on my insecurities?