Feeling lonely, how can I strengthen my relationships?

I feel a bit like I don't have friends, thats not true I have a lot of friends. I do feel like my best friend and I aren't really close anymore though, I hardly see him but thats because of college and exams which is fine. But he sees this other girl who is my friend too but it kind of bothers me because he sees her yet doesnt ask to see me. I don't know if he invites her though or if she organises it. He's never organised anything really. I have some younger friends that id like to see more of outside this club I go to, the summer holidays are coming up, how can i invite them to go out and do things without seeming weird? I just want to be happy and be with friends again. Ive been studying a lot and my older ones have too. I will meet new people in a year when i leave to go to university. I will be looking for a job now too and i am joining a new club with adults. I find it hard to fit in sometimes and get a bit depressed about it. My other close friend is a bit annoying sometimes, she has anxiety issues and she doesnt really seem to care sometimes when i try tell her about my problems she just talks about herself. Do you think id be able to strengthen my relationships in the summer? Should i meet up with friends I've not seen since school? its been 2 years.