Jealous SO

So back story- I have been with my SO for almost 3 years. I absolutely adore him. He is my best friend. My everything. He treats me so well and we have been through a ton together and always prevail. HOWEVER, he is very jealous. It never usually bothers me because I don’t have many friends/ guy friends so whatever. Buuuuut- in my past (before him) I have hooked up with girls. I am 100% straight but a very sexual person that enjoys pleasure and experimentation. He knows about this. He hates it. Now it’s to the point where I can’t even text my female friends or female coworkers without him thinking I want to fuck them!!! I don’t! I only want him! He is tall and super handsome so why he would ever he insecure I will never understand but clearly he is. How can I fix this! I only want him!