How to cope with my jealousy and insecurities?

I have been insecure and jealous since I was little and sad to say not sure how it started, I know where although. It started when I got teased in grammar school and no one like me and thought I was ugly. I was always outcasted. I was too embarrassed to share how I felt with my mother. Ever since I kept things bottled in, afraid to open up or be confident, but my mothers was my escape. She was my best friend and we did everything together. When she passed away when I was twelve, I felt alone and unprepared. It affected me with standing up for my self with friend and family and I would make myself suffer. I can't trust and feel everyone is against me even in secrets. My current fiance challenges me the most. I had a crush that grew over the years we were friends. We been friend for 9+ yrs and finally hot together for 8 months now, but he use to b a man whore, had lots of women, I knew but always kept quiet because I weren't his, but was jealous and insecure because he made me feel special but always had another and described them in ways I thought I couldnt match. Now he is faithful, hut him and some of the women are still friends and it bothers me so much, i told him but can't tell and scream how I feel all the tile, because sometimes it ended in an argument. I'm Jus so lost and not in love with myself that I don't know how to start. Everyone says to recognize, investigate, calm down, talk and cope, I've done all of that but that doesn't tell me how to be confident and love my self 100%. I wanton outlet, singing.g was it but now so afraid, now I feel only to write. I don't want a shrink. What to do?