I'm starting a new school in the fall and I'm panicking

I'm changing schools next year, and I really need some advice to help get less socially anxious over the summer. Right now, I have around 5 close friends and when I'm with them (1 in particular) I feel so much less social anxiety. It's still there, but it feels easier to be natural with strangers when she is around. When none of my friends are around, I'm a complete disaster. I can't remember the last time a made a friend without her around. I'm constantly afraid I'm making people uncomfortable whenever I open my mouth. It's not even that she talks to the person, she just feels like a safety net when she is standing nearby, and it makes it easier to have a non-awkward conversation.

I've been trying really hard in the past few months to be more outgoing, and I truly think I have gotten better, but I'm afraid of what will happen when she's not even in the same city as me.

People tell me that the best way to be more outgoing is exposure therapy, and that is what i've been doing, but just baby steps at the moment. Talking to friends of a friend, asking simple questions, making remarks in passing to people I semi-know.

I'm afraid of the two biggies next year: Talking to a big group of people that are already friends, and talking to people of the opposite gender I find attractive (It sounds so stupid, but even though I generally don't have crushes on them it's so much harder to not be awkward!)

Does anyone have any drills (I don't think that's the right word) that I can use to become less socially awkward in a new place? Or any advice in specific about these two scary groups of people? Thanks in advance for any replies!