How to get rid of this loneliness feeling?

I feel so left out when it comes to friends and I've been suffering this emotion for a month now and I really want to end this. I am now at the state of getting doubts if whether I have true friends or not and if I believe in myself or not. I wish someone could help me. I've been visiting my school almost everyday now even though its summer vacation for us here in Philippines and each time I visit my school I usually get the feeling of being left out because we all know that the friendship starts inside the school campus so yeah... i was trying to reminisce the good moments but I didn't get enough good moments because I feel regret as well. Due to the fact that I backed out as a CAT applicant of being an officer and Amity member, I've been getting this regretful feeling as well. i feel so left out that I don't trust my friends because each time we get a group project, it seems that they all give me the things that needs to be done. During my 4th quarter, I sticked to the same group members with different subjects we handled and so far almost all of them did nothing. We had 6 subjects and everything was due on a two consecutive days and we were running out of time so i had to work on it not just for me but for them as well. help me I'm so confuse right now. I think the problem to this situations is that I'm too selfless ( my parents told me so)