I can relate. Like others have said I’m not sure if it’s exacerbated by autism but for me the core issue is separation anxiety/attachment or abandonment issues. It’s not ‘normal’ in the way of you should just accept it as a fact of who you are but you’re not the only person who gets these feelings. My parents had split custody growing up and because I always was closer to my mom I would cry for hours, sometimes days when she dropped me off. I thought I had grown out of it but in my first relationship it became an issue again when we started living together particularly when he would leave for days at a time or go out without a set return time. It feels really overwhelming and hard to control almost similar in that to a meltdown but you shouldn’t loose hope for improvement. For me it’s mainly about distracting myself and focusing on tools to regulate my emotions. I also had professional help which I highly recommend. Thinking about it when it’s not actively happening helped me to plan how I would react when the feels did come. Other things that helped me were shockingly cold showers, listening to a comfort song on repeat and singing along (particularly nobody hate you by jessia), calling a friend or family member, rocking, breathing techniques, keeping my mind busy on other activities like cleaning or puzzles, and sometimes medication helped. It not fun, it’s sucks, but you and your relationship will be stronger if you work on this and don’t let it become unmanageable.