Jealousy issues, how to fix?

Today after something happened I started to think about how jealousy impacts our relationship. Both my boyfriend and I are very insecure and jealous people and I want to fix it. Currently we have an unofficial "rule" set that both of us shouldn't talk to the opposite sex due to our jealousy. This went fine except that he had some female friends and I had male friends. The rule wouldn't work so whenever we ended up talking to someone else one of us would be jealous & petty.

For example, today in class I was talking to some guy friends, let's name them A&T. We do not talk outside of class & do not text, nor did we ever have anything in the past. T, I've known since elementary school and A for about a week. I posted a photo of them with their hair up in class because they're my friends and I thought it was funny. My boyfriend saw it & got really jealous because I was posting something on my story with other guys. He sent me a "k, ly2.." to tell me he was uncomfortable. I reassured him nothing is wrong with me having guy friends in class. I understand why he was uncomfortable, especially because of jealousy, but honestly it's just been a bit too much.

I'm not saying he's the jealous one, I am extremely jealous too. He'll mention an ex and I'll crumble. I used to check his exes & past sexual partners social media regularly and compare myself. I have even broken into tears because of my jealousy. I'm aware of it and I know I need to calm down and take a hold of reality. I've been working on it.

Another example of his jealousy is every time a guy texts me (usually asking who I am because of quickadd on snap) he'll immediately say"who's that?" & tap on the message. For example,my friend J texted me and he said hey. He and I don't have any past together and hes one of my old online friends.

What can we do to aide our jealousy? How can we fix it? Thoughts?