Can't pinpoint what exactly is wrong with me, but it's affecting my relationship

I'm hoping that someone can help me identify what my problem is (like, is it something psychological? Do I need to talk to someone?) so I can go about solving it.

I'm 21 and got into my first serious relationship about a year ago, and over the past couple months, I keep ending up in ridiculous fights/disagreements that can kind of all be boiled down to me acting carelessly and not realizing it until it's too late.

The general pattern is: I say or do something illogical (like nothing that would provoke any anger/sadness outright, more just something that causes confusion) -> my boyfriend reacts accordingly, taking what I've said at face value -> I can't explain why I did what I did, but start verbally floundering trying to justify it -> it becomes a full-blown argument.

For example, today my boyfriend and I each bought a book and were keeping them in the same bag in his car. I asked him if he wanted to keep his book in our apartment, and he said yes. But then for some reason, I told him I'd take my book inside and leave the bag with his book in the car. I had literally no reason to say this and I still have no idea why I did---it wasn't any sort of inconvenience for me to carry the whole bag in, and both the books needed to go into the house anyway. So of course he was confused and then everything escalated into a fight.

It seems like I find myself in situations like this again and again. I try to be alert and hyper-conscious of my words and actions, but it still just keeps happening. I don't know how to fix this issue or how to talk about it because it doesn't make any sense for an adult who's in complete control of her actions to be acting this way.

I realized that this is also an issue I had with my parents as a child (not thinking before speaking/acting). They love me unconditionally, but with my boyfriend there's the risk of him reaching his breaking point and not wanting to put up with this behavior anymore---so I need to do something about it, but I'm not sure what.

Is there something wrong with me cognitively? Does anyone have people in their lives who act this way, or a perspective on how to stop being like this? Would really really appreciate some advice.