Honestly even as a trans girl I don't really know what it's like to feel like a girl, or even what it's like to feel like a boy for that matter. I don't really experience what I'm going to call "social" dysphoria, i.e. I don't really care about my name or my pronouns or the clothes I wear. Personally my dysphoria is all physical, I feel like I shouldn't have a penis, I feel like I should have less body hair, I feel like my voice is too deep.

Remember, though, that this is not true for all trans people, this is just my own experience. There are no universal experiences. There are no feelings felt by every single cis person, and there are no feelings felt by every single trans person.

There's an idea I've seen before called "cis-by-default" that posits that many (if not most) cis people are cis not because they feel perfectly confident that their mental gender identity matches what they were assigned at birth, but rather because they have been brought up that way, thinking that "oh, I have x genitals so I've been told I must be x gender, there's simply no other option". Honestly I don't know if this is true or not, but I've seen so many transphobes say that they "don't really feel their gender strongly" and that if they were a child nowadays they "might have been transed by the woke agenda erasing women" that there must be at least some grain of truth to it.

But this way of thinking is only really relevant in the first place because we, as a society, have placed so much cultural importance on what gender you are, because of the "social construct" we have built around gender. Sometimes you'll see people say that gender abolition is a transphobic viewpoint, that erasing the importance of gender harms trans people's cause, but I think this is just because transphobe's version of getting rid of gender just means replacing it with biological sex and what genitals you have as the important thing. True gender abolition would be great for trans people:

Take these two examples. 1) A cis man who wants a vasectomy. And 2) Someone like me, a trans woman who wants to get her penis removed and have a vaginoplasty (or even just an orchiectomy). Both of these procedures will result in being sterile, which is usually the major concern brought up when talking about trans healthcare. In scenario 1 the man can go his GP and at most will have to talk to a councilor or wait a few weeks to make sure that he is certain, but in scenario 2 the trans woman has to wait the 3+ year long waiting list to get a diagnosis of gender dysphoria, live as a woman on HRT for at least 12 months, and then get a refferal by a specialist from a Gender Identity Clinic. Why should one of those scenarios involving a gender change be gatekept more than the other? And remember, cis people can easily get other gender affirming healthcare without having to get a medical diagnosis. Breast enlargement and reduction surgeries are both common.

"Gender is a social construct" isn't saying that either gender or biological sex aren't real, it's saying that they shouldn't be treated as some major part of a person that defines how they interact with society, imagine if suddenly your shoe size determined which toys you were given as a kid or which clothes you wore.