My girlfriend (26F) gave me (24M) ultimatum

We have been together for only 5 years and she told me she wants to marry at 28 latest since she wants to have children at 30. She sent me pictures of engagement rings so I don't get them wrong and gave me her ring size. She even said she is happy to pick the ring after I propose to her.

Currently I feel pressured I think I am too young to marry. She is my first ever girlfriend and I love her. She is beautiful, smart and sexy. I feel like sometimes I don't even deserve her. But I am not ready to get married yet.

I was thinking of getting married in our mid-30s and I voiced that out, she said it's too far away and her fertility might fail since she has PCOS she is anxious about getting pregnant. Though we talked about this and she is open with adopting or no kids. She told me we might have a change of heart about kids in the future so she at least wants to secure the possibility since adopting is expensive.

In 2 years we will be 6 years in relationship and she told me that is enough time to know if we are ready to get married. She cried that if I don't want to marry then I shouldn't string her along. But I am not stringing her along, I want to marry her too but in the future, I am just not feeling it right now since my salary still isn't good for marriage although her salary is way higher than me.

I still think I am not ready though yes I don't know what will happen in 2 years… I just feel pressured and it turned me off.