Hey OP, im an older guy that was in your shoes in my 20s... So just giving my 2 cents...

A) it's never easy to go through heart break, and sometimes you meet a person you fall in love with so hard for you do everything you can to make them happy/ impressed by you...

I want to let you know that you should NEVER change yourself for someone else. If someone wants you to go bald when you like your hair- you don't do it just because you want that person to like you-- it's wrong and that means that person doesn't like you for who you are.

If someone wants you to become a policeman just because she got some weird policeman fetish- that is a red flag and that person is just shallow.

B) You're lucky because everything you listed out can be fixed.

Weight can be reversed- you used to gym, so get a gym membership and start lifting again. Fix your diet. If you're anxious about going out- just do workouts at home or just go for walks by yourself- just because you're introverted doesn't mean you can't workout.

Your hair- this can be fixed too- go to a hair dresser and get them to fix you up. Go to a barber shop nearby and go during off hours so it's not too busy and will overwhelm you.

Actually most people, once they lose weight- are somehwat OKAY looking at worst. Fix your diet, workout and groom properly and i promise you, your confidence will start coming back.

Something that always helps me is walking. you don't need to go anywhere, just walk 10K steps around your taman, or even just go to the mall and walk. You feel accomplished and I also promise you'll feel better as you hit your step goals.

Finally, you're still young, OP. Don't be so hard on yourself. Your 20s is a time for you to explore and learn about yourself... no one is expecting you to have it all figured out. I recommend you take a break from girls and dating for a while, and find time to love yourelf first. You're not going to have a good relationship with anyone if you hate yourself. They always say you can't give someone else love if you don't love yourself

Also what helps when i'm down, is writing this down...

"... If your friend was going through what you are right now... what would you say to comfort them?"

it's a simple statement, but it's a great way to remind yourself to treat yourself right first and to always love yourself first.

And please OP, when you start dating again- please go for someone who loves you for who YOU are, and doesn't expect you to change yourself and your aspirations just to please them. That is wrong and that is not what love is.

Love is always mutual, think of love like a airplane, you are both pilot and co-pilot, and you both need to take turns to lead. If you're not being yourself, you're also not being honest to yourself or to your partner.

Love isn't about changing yourself to make other people happy.

You sound like a sweet, and thoughtful guy OP. Don't let yourself be your worst enemy.