Why do I feel so sad when i am ignored by my collegues ?

Maybe you can tell us a little more about the situation. What's your job? Is it office work? How often is the interaction between you and your colleagues when you are working? How often do you talk to them? Do you only talk to them about work? Is there ever a chance you talk about things other than work, like hobbies, likes and dislikes, personal stuff? Also, are these six (or five?) people your only colleagues? Are there other people in your company?

Learn to say "I like myself as I am." I feel your pain since I have to deal with some people on the internet who claim to be my friend as long as I am their yes man. Like WG Ventures which is a company making a cartoon named Wordgirl Advance which should be on the internet in the fall of 2017. They like my fan fictions but only if I allowed them to control my original characters which was my biggest mistake.

Do not think that you are loser or stupid, believe me people have strange reasons to ignore and hurt others. There are numerous examples where a friend or loving mate has left someone who did everything to make relationship work for no reason. Relationships are complex, its better to move on rather than feel sad about something which is not in your control. Let them be and find new friends.

You may have to move on. Sad but true. Just do the work and socialize elsewhere.

Is there at least one person in the group you can trust? If so, I'd talk to this person about the impression you have of the group and their attitude towards you. Maybe they don't realise that they exclude you all the time.

Have you asked them?

They don't exclude you or you wouldn't feel among friends there at all - you could try widening your social circle, or organizing a social event and inviting your friends to it, also talk with each of your friends on a one to one basis rather than in a group environment - good luck

It happens to many people but very few people express their disappointment, you see its not you. Case 1- I think like a businessman and team mates think like poets and authors, now I will think , its the money which runs the whole World, so I am the most important one, if not important the atleast recognized person in the team, but it does not happens. You can be the somebody very understanding caring, kind person but if there is no need for a person in that place then you will be invisible for them.You see diamonds are expensive not because they are rare but because demand is more than the supply and most importantly there is need for diamonds, others wise they pieces of carbon. Case -2- This is about similarities , if they find you are not their type then either you change for them or they change for you. Case- 4- Every member in the group or team is so occupied with their stuff, that they dont realize that you are left out, your senior intervention is required. Case- 3-Something really went wrong, may be you have to speak to your boss or employ relation person. Best of luck.