love him so much il lose him

hi
bin going out with my man for 2 years. hes my 1st real bf. i ADORE him. n he ADORES me. its so cute, except for 1 thing. im quite insecure, even worse on my period. thers no need to be, neither of us hav cheated or anything. i go in a mood wen he even hints at talking about an ex. at its worse i get in a mood wen he just mensions a random girls name!
he's completely understanding but i know that if i dont do something about it il end up pushing him away.
im so worried about losing him even though he thinks the world of me and would never leave me....what the hells my problem?!

i used to just say that its my first real relationship so im naturally freaking out...but it should have stopped by now. i need to trust him but i just cant...i dont know how to.

i dont read messages on his phone or keep checking up on him..but i can imagin if i dont get help i will in the end.

PLEASE HELP US!

thank you