Why so I feel so awkward around friends / people I know?

I'm 18. I don't have many friends because of this.. I usualy just hang out with my 3 close friends and their other friends. When I'm with my close friends, I sometimes feel so awkward, like not knowing what to say, not feeling relaxed or comfortable. When I see people I know, like friends of friends it's awkward too, I feel so much pressure with small talk and just this weird awkward feeling. I have a boyfriend and I'm so comfortable around him, I never feel awakard. Why is that ?