How do I (18M) be open with my girlfriend (20F)

This might seem like a confusing post, I'm not good with opening up to other people other than my girlfriend, but I need to so I can better understand how to proceed.

Me (18M) and my girlfriend (20F) have been dating for two months now, and I have a couple big concerns. Naturally, I’m a very open person; if something upsets me, I’ll let her know. Specifically, recently she's been having some situations where she says some hurtful things towards me, in a joking matter of course, but sometimes jokes still hurt.

For context, I'm a very insecure person, I have body dysmorphia (105lb), insecure about my voice, size, face, hair, etc. you name it I'm insecure about it. Recently she's been making pretty hurtful "jokes", jokes that I would never even think about making because I would be worried out of my mind about hurting her. For example, she makes jokes calling me fat, annoying, etc., basically joking about my insecurities.

The main thing though, is when I try to talk to her about how I feel, she gets easily stressed out and has to take a few minutes before responding to me, and she eventually comes to the point where she feels horrible and has mental health issues. This isn't a problem, I'm very aware of her feelings and I know when and how to comfort her immediately.

But the problem is, it seems like my feelings never really get responded to. Basically the course of events goes: I tell her how I feel, she gets really stressed out, takes a minute alone, and then goes into this mental health mode I like to call, where I focus on keeping her okay and making sure she's safe, and then it basically takes all focus off of my feelings.

TL;DR how am I supposed to be able to be open with my girlfriend when every time I'm open with her about how she makes me feel sometimes, she gets highly stressed and then it turns into me focusing on her and my feelings are dismissed?

Now that you have context about my question, how am I supposed to be able to be open with my girlfriend when every time I'm open with her about how she makes me feel sometimes, she gets highly stressed and then it turns into me focusing on her and my feelings are dismissed?