Don't let the opinion you have of yourself keep you from living the life you want. You will never get these years back. Nobody is going to laugh at what you look like on the beach if you join your friends on this trip this summer, but you WILL regret spending a whole summer of your twenties looking at a computer alone in your room.
Motivation makes you feel good, discipline gets you ahead.
Loving yourself is like handing the menu when you're waiting table. If you don't have it, you can't deliver. Get to know yourself so you can show people what you have to offer. If they don't like it, they'll get lunch somewhere else and you won't end up trying to make a fucking burrito to please them when really you only serve pizza.
Go on adventures. You will probably have to by yourself. But guess what, you'll have higher chances to meet someone to join you than by staying where you are. Plus you'll have stories to tell.
You will never find out what you want to do with your life by sitting there wondering what you could do with your life. You don't have to prepare for your life, your life begun 20 years ago. Do the things you want to do now, that's the way to figure out even more things to do and to allow things to come to you.
Trying to look like that hyper sexualised photoshopped pre-teen who modelled for that ad would not make you attractive. It will make you miserable because you are bond to fail and it stops you from focusing on what is really important and what will make you really happy. Don't participate in alienating and oppressing yourself. Be stronger and smarter than the people who tell you you're missing something you can buy. You're not a work in progress, you've cooked for 9 months, you were born ready. Focus on being the most interesting healthy and happy motherfucker out there. THAT will make you attractive.
You don't get a SO by desperately wanting to lose weight, not even trying and feeling miserably and sorry for yourself. You get a SO by meeting people, figuring out the kind of people you like, talking to them and creating bonds and relationships.
Try! Anything! Do the things that you are scared of. It might fail, but and the end of the day you will be more knowledgeable than if you had not tried.
Perfection is a lie, seek happiness, light, love and warmth, be kind to others, you got this.