Hi, I know exactly how you feel, I hope you're feeling better and are getting some rest !!

I used to say this sentiment to my bf/FP, but long story short, he's the kind of guy that needs me to tell him my needs because 1. he can't read my mind, nobody can and 2. sometimes he won't realize something is important to me, and prefers when I just come out and say it instead of playing games and expecting him to know exactly what I want. It's worked out great for us :)

I think you should tell that person that you have abandonment anxieties and "getting left on read" triggers that for you. You guys can set boundaries together, and one of them can be: letting each other know when you're busy and may take extra time to respond. Or something along those lines. But, you're also right in the sense that a relationship is 50/50 and you can't do any more than your part.