Help,feels weird????????????????????/?

Ok,yesterday I took my dog for a walk when a saw one of my clmates John cycling. I said Hi even thought I don't really like him but I didn't want to be rude. He said hi and he asked me how am I doing at my exams. I said great! And I aksed him and he said good. He asked If i am ok and I said yes. Me too he said and then he said that he had to leave and he said bye.I said bye too and left. After I felt weird...... I can't explain it I felt somehow admired,happy but also sad,weird and angry. Weird! John has a girlfriend which is a friend of mine. In the past I used too hand out a lot with her but after I lost contact because we both go High School and we are very busy. So I just say hi when i see her and I feel somehow bad. Also weird! I have also seen the being together (my friend and John) and kissing and feel very very bad and sad and angry. I felt like he was hitting on me and that felt nice but uncomfortable beacuse he is cheating his girlfriend and I feel bad. While I was going home i saw George, which is 2 years younger than me in his garden with a girl gold Alexia and when I saw her I feelt angry, like I wanted to hit her ithink because she was with George and I wasn't. When I see George and talk to him I feel weird and nervous! Why am I felling all this? Help. (I am a teenager and I don't have a boyfriend.)