Speaking as a man, let me say that women in general are their own worst critics in matters of physical appearance.
Second, let me address one aspect of your post that I know is 100% not true. 25 is NOT old. 25 is young and in your prime. 25 is a great age, you are still young enough to hang out with 21yr old hipsters yet old enough to not be considered so wet behind the ears by those of us 40+ yrs old.
The other great thing about being 25 is that you still have loads and loads of time.
As for being ugly I can relate. You see, growing up I had the absolute worst Acne known to mankind. My acne was so bad that calling me pizza face would be an insult to pizza. I had giant dime sized and nickel sized boils on my face to go along with my acne. There were some days my skin was so bad that I would literally cry... keep in mind I'm a guy. That is how bad my face was. There were days my skin was so bad I wouldn't go to school.
The only thing worse than that was the comments and advice I'd get from everyone on skin care, what soaps they used or acne medication... seriously as if I didn't try!!! I can safely say that in the entire history of mankind no one has tried more soaps, cremes, lotions, and medicines on their face than I have. I even kept journals trying to figure out my skin, trying to correlate my good skin days to foods I ate. Nothing worked!!!
So what did I do? Well, I became the most funny, witty, romantic, and charming guy on the planet, basically, if I couldn't look good on the outside then I guess I better look good on the inside

. I also got in world class physical shape. I had a perfect 10 body, six pack abs, and all my muscles were cut like diamonds.
I also found a soap, wash, skin routine that reduced my acne from horrible to just "bad". I know, that doesn't sound like much, but after a life of being pizza face, just having normal horrible acne was a step up.
Then, when I turned 25 something miraculous happened. I stumbled across a late night infomercial for Proactive Treatment. I didn't think it would work, I thought it was fake, but when you have skin as bad as mine you will try anything so I tried it, and wow, I went from bad acne and boils to "almost" clear skin. I literally cried. Of course, my face still had years of acne scarring but man, just to have a face that wouldn't scare small children and make people do a double take was awesome.
So, back to you. You are 25 and hate the way you look. Firstly, I would divide it into 2 components, things within your control and things not within your control. Weight and skin complexion are within your control (I have no idea what your weight and body type are). Another thing within your control is personality and inner beauty.
I know I don't have a clue as to what you look like, but I would hazard a guess that though you may not be a perfect ten model, I would guess that you have potential to be "pretty enough".
What does "pretty enough" mean? Well, unfortunately, you women have been brainwashed into thinking that you have to be some perfect 10 super model or else you are ugly. And that isn't true. The truth is, we guys are very easy to please in the looks department. Sure, we may talk a lot of crap when we are with our friends when we are rating girls that walk by. But the truth is, we guys are attracted to a wide range of girls body types.
No matter how you look, there will be a subset of guys who find you physically attractive.
The other thing in terms of attractiveness to men is something I will call the Mae West Factor.
Mae West was a sultry brazen feminine type hollywood star back in the 30s and 40s. She was one of those women that knew how to wrap men around her fingers. It's kinda like a female Jedi mind trick and there is a very small percentage of women that know how to do it. And this has NOTHING to do with how you look. It is all in the attitude.
When I was in college one of our sports trainers had it. She was 5'5" and 160 lbs. She was not a small woman by any stretch and definitely on the big side. Her face was very plain, her body type was not voluptuous or anything like that. Physically she was nothing special. But man, she had every single one of us guys wrapped around her finger. She just oozed raw natural femininity and female power. There was just something about this woman that every man couldn't help but notice. She was fun, outgoing, sultry... it's hard to explain...
So I guess the point of my rant is this.
#1) You are 25 and very young, you are in your prime actually and have tons of time so don't feel desperate or anything
#2) You don't need to be a perfect 10 model to get guys
#3) There are things you can do to make yourself feel more attractive and be more attractive
#4) Attractiveness isn't just all about looks, there are other components as well
#5) Even if you aren't as attractive as you would like, don't let that stop you from pursuing your goals and dreams.
Even when I was at my ugliest, I still managed to land pretty girlfriends. So there is more to it than just looks. Not to make this into a post of getting a girlfriend or boyfriend. My intent was simply to say that your outlook isn't near as bleak as you may think. There is still hope and you have tons of time. And even if your physical looks are beyond your control, so what. There is more to attractiveness than purely physical looks.
I hope something in this ranting has helped.
Good luck...