Please give advice if you feel able.
For reference, my pronouns are they/them I just use the term girlfriend because of the stereotype. 

I hate this. I hate feeling like I’m crazy for this stuff, when in my mind it all feels so rational.
Today my partner has been busy, which is completely fine normally. The issue is that they’ve been distant all day and didn’t really give me any heads up/tell me. I have no limitations about what they do or where they go because they’re there own person and can do what they please, I just always ask for my anxiety that I get a little response. I don’t even ask for details if they don’t want, just a message letting me know they’re gonna be doing something. This isn’t really a jealousy issue, as I’ve never been a truly jealous person. It’s just an internalized fear of abandonment. They haven’t texted me at all, or read my messages since earlier today. I know they’ve been on their phone, because they’re posting on social media. I know it’s irrational, but the fear of being ignored, abandoned, or replaced kicks in. We’ve had conversations before about how my fears and nerves would be eased if they would just send a simple “hey I love you I’m gonna be busy today” text, and they’ve said before they totally understand. But they just don’t follow through. 
They haven’t texted me in 4 hours, and posted a video online 20 minutes ago. I sound crazy, I know I do. But in my head it’s so rational as to why I’d be upset. I don’t know how to get over this. I don’t know how to NOT get so irritated and upset. It’s gonna take so much of me to not bring it up later too, and then I feel like I’m sitting in it. 

PLEASE give advice. I do not know how to calm this “crazy” partner feeling.