YANBU. It is actually commendable to not have children if you don't want them. The world is overpopulated and IMHO, many of the messed-up people out there are messed-up because they were unwanted (my Ex was abusive and it's pretty clear that this was the reason for his issues - his mother used to openly chat in front of him about how she never wanted children and always regretted being a mother, like she was discussing the weather, the cow). 3 of my and DH's closest friends do not want children and, in fact, we set two of them up and they are getting married this Summer! They are great with our kids and others but don't want their own, end of story.
However, this does sound more like the problem is that you have extreme anxiety and the focus of that anxiety has become about pregnancy and childbirth. No doubt something in your past couple with your cultural pressure to be a mother has made it the focus. I think you would benefit with some counselling about the issue. Not just to sort out how you truly feel, be that not ever having kids or you do actually want them but feel overwhelmed by your anxiety in many issues about it all, but also to deal with the extreme anxiety and phobia in themselves. No-one should be carrying around that much stress and upset, you poor thing.
Stop worrying about what others think about you or expect of you. At 25, you are very, very young. To me, anyway! I had my child at 40. Perhaps in your culture you are expected to have children younger, but again, you don't have to follow those rules. You have at least another decade before you have to worry about your fertility waning. I hate be a patronising old biddy but how you feel at 25 and what worries you then is not what you necessarily feel or worry about when you are 35, or even 30. Trust me.
If you feel like you would have kids but don't want to go through pregnancy and labour or be a SAHM, then work on that. You are young enough and driven enough to really concentrate on your career and make a shedload of cash. Which you could use towards using a surrogate, an international adoption (I don't know if your culture is from another country where poverty is an issue, but if so, you could adopt from there, say), or have the best private care and an elective CS if you decide to get pregnant. And you do not have to be a SAHM. I am a SAHM and love it, but would never, ever suggest that someone else do it if they don't fancy it.
As for the complexion thing then, hmmm. I hate to break it to you, kiddo, but the face will not stay perfect forever. I've always had great skin - I am that rare thing, a ginger with no freckles and no propensity to early wrinkling - but I am in my 40s and time has taken its toll. It's still better than most people of my age, if I am allowed a moment of vanity, BUT it cannot compare to my 25 yr old self. It would be daft not to get pg because of your complexion, although I know that's not really your reason, you're just fixating on that (I suffer from anxiety, I know how it works). I have never known anyone get melasma. I know that Kirsty Allsopp got it and it went away (my mind seems to store trivia!). And when I was pg, my complexion was the best it has ever been. Ever. I looked like an airbrushed teenage model! The rest of my looked bloody awful mind, and yes, I had hyperemesis, stretchmarks and am still working out the babyweight nearly 2 yrs on, but it was worth it.