Need help understanding my partner's behaviour

Hi all,

I'm hoping to get some help from people who may have experienced something like this. 

My partner is autistic, and I love her very much. We have a wonderful life. I try to be as supportive and understanding as I can, in most cases she's good about letting me know when she's feeling overwhelmed. I've identified a lot of things that could upset her and I'd say that most of the time, we're just like any other couple. Its wonderful.

Mostly.

The problem is that there are other occasions when she can switch very quickly and behave in ways which are very out of character. She can be reckless, impulsive and very selfish, showing absolutely no regard for my feelings. And when I explain how I'm feeling, it always seems to be thrown back at me. Her behaviour is perfectly reasonable - I'm the one being insecure. Or having very fixed views. Sometimes I find myself feeling gaslit. 

It's hard to be more specific on an open discussion page, but I'd welcome the chance to talk with people about this. I love my partner very much but I often feel both insecure and undermined by how they treat me - they seem to understand that what they're doing can be very hurtful, but then do it anyway.