You want to learn to value yourself more? DO IT! Give yourself something to value.
Go get a haircut,use mouthwash and brush your teeth,go shave and take a shower. Then from there head to the mall and go get some clothes that you like no matter what the price,get three or four outfits. Get a new pair of shoes that nice and classic,ie K Swiss Classic. Now go get some NICE colognes off of eBay,Chrome,Sexual or Ignition will do the job.
Now you should immediately notice changes in how people look at your after that. Now work on your body posture,back striaght,chin up and chest out. Walk like you should be,A PROUD INDIVIDUAL!
Always remember,be positive,smile and meet new people on a daily basis.
Now if you are happy with yourself and want more,HIT THE GYM! You dont have to be a 250 lb. gorilla. just gain some muscle. Once you gain that you will see how easy it is to gain muscle and want more,its a cycle. Now if you want pointers at the gym I can help you there,and with a diet and so on. TRUST ME ITS EASY,you just have to have some dedication.
Good Luck!