i absolutely relate to this!! my romantic partner is also my FP and i struggle with this as well. usually, when i start splitting, i want someone to Know that i’m upset, usually my FP. and i want them to know it’s their fault and make them feel bad. usually, instead of contacting them or talking to them, i acknowledge the split and take some time to give myself space and cool down, while typing all of my thoughts into a notes document. then i throw myself into a distraction for a while, which usually quickly diverts my attention, and when i go back to what i typed before, it usually seems ridiculous after the heated moment has ended. tldr, its important to Acknowledge the splitting and let your partner Know about the split before allowing yourself space to process those feelings. good luck friend!

I am the exact same way, and my best strategy I try to use is to alter my thinking, I remind myself that I can't control how others feel about me and that worrying about it will not change anything. And just try my best to focus on how much I love my SO and try to live in the present and enjoy the time I have with him. This of course isn't a cure all and doesn't completely fix those insecurities but it has helped me quite a bit to in a way take the edge off. And of course communicating how you feel to him is very important but it sounds like you are doing your best there.

I think in the beginning, my husband was my fp, but now idk. It's been 22 years together now.