Girl's Behavior

Why do I get so nervous around him? How can I relax?

So there is a guy I like, we have known each other for a couple months and have gotten along great. The problem is that the moment I started developing feelings for him, I kinda changed how I act around him (unintentionally). For example, when I just thought of him as a friend, I was able to be completely myself, all comfortable and funny and joking all the time, being all touchy-feely and just fun to be around. But ever since I started having feelings for him, I feel so weird and nervous around him. I am no longer as flirty or outspoken, because I am always afraid he will think I am desperate. I am always scared I will say or do something wrong and he will get the wrong impression of me. What is even worse is that we have a mutual friend (girl A) and she has a boyfriend, so she manages to be friendly with everyone because she just treats them as friends. I think my guy is starting to crush on her (yes, even though she has a bf), because she is so chill and comfortable with him. And basically the way she is with him is how I am with all my other guy friends, I know I can be that way, but with him it's just different. I freeze, I feel like nothing I say comes out right, and I just don't know how to relax around him and just not care about what he thinks and just be myself. Sometimes I am so nervous I will purposely avoid talking to him or sitting next to him in a group setting. I don't want him to think I am avoiding him though or that I lost interest, because it's the opposite! How can I become more like myself and less like this scared little girl? I just want to relax and go back to being "normal" around him. And please don't just say "Oh just get over it and do it" cause it's not that easy... Any methods anyone used that worked for them? Help please :)
Why do I get so nervous around him? How can I relax?
Post Opinion