Praise be to Allah.
Faith becomes weaker as a result of neglecting obligatory duties and doing haraam things. So long as you are doing your duty towards Allaah and heeded His prohibitions, your introversion and keeping away from people, and your fear of them,  will not harm you. But if your fear keeps you from doing any obligatory duty then you will have committed sin thereby, for example, if your fear stops you attending prayers in congregation in the mosque, or stops you denouncing any evil action that you could change by speaking out or taking action, or stops you from offering advice that you should offer to those who need it. 
You should not give in to these fears or accept them, rather you should look for the causes and try to deal with them. It may help you to know that created beings have no power to bring benefit to themselves or to ward off harm, rather if the nation were to gather together to benefit you in some way, they could not do so unless Allaah has decreed that for you, and if they were to gather together to harm you in some way, they could not do that unless Allaah has decreed that for you. The pens have been lifted and the pages have dried. 
Everything is in the hand of Allaah, and He is the One Whom you should fear and put your hopes in. The criticism of people has no value and carries no weight; it is sufficient for the believer to attain the pleasure of Allaah even if all the people are displeased with him. 
Whoever adheres to the command of Allaah and persists in doing so, is the most honoured of people, for Allaah has decreed honour for His believing slaves. As Allaah says (interpretation of the meaning): 
“But honour, power and glory belong to Allaah, and to His Messenger (Muhammad), and to the believers…”
[al-Munaafiqoon 63:8]
The effects of this honour should be manifested in the believer’s words and actions, in all circumstances. He should speak up for the truth, offer sincere advice, remind people and teach them. His approval and anger should be for the sake of Allaah, and he should only get angry when the limits of Allaah are transgressed. 
This is what a person will be able to do when he becomes aware of his role in life, for he is commanded to worship Allaah and to convey and spread His religion as much as he can. This means that he should mix with people and bear any annoyance they cause with patience, especially close relatives. According to a hadeeth narrated by al-Tirmidhi, 1307 and Ibn Maajah (4032) from Ibn ‘Umar, the Prophet (peace and blessings of Allaah be upon him) said: “The believer who mixes with people and bears any annoyance they cause with patience, is better than the believer who does not mix with people and does not bear any annoyance they cause with patience.” (This hadeeth was classed as saheeh by al-Albaani in Saheeh al-Jaami’, no. 6651). 
Perhaps you can start to get to know some righteous friends with whom you can feel comfortable and secure, who can help you to overcome your feelings of fear of people, and this will help you to find the sincere brotherhood, good treatment, clear goals and sincere intentions that you are missing in the people around you. 
We also advise you to go to a doctor who specializes in treating psychological illness, perhaps he could help you to solve your problem. 
We ask Allaah to help you and give you strength.